I have an older Mac with Snow Leopard OS. Keep getting blocked plug in. Need to install Adobe Flash, but don't know how.

Follow the instructions where it says: Learn More here > About Safari 5.1.7 and Leopard Security Update 2012-003

You need to be careful about such warnings. You should ONLY download the update from Adobe, not from any other site. If you already have some version of Flash installed, check your System Preferences. There should be a preference item in there for Flash. Updating via that preference item is a safe way to proceed. The update will be downloaded to your computer, probably to your Downloads Folder. You will have to open the downloaded file and install the software. It's a simple process.

You'd be better off using Firefox rather than a very old version of Safari, which cannot be updated anymore except via a major OS upgrade.

Here's the direct from Adobe link: https://get.adobe.com/flashplayer/otherversions/

You need the NPAPI Plug-in version 21.0.0.213. You don't want the PPAPI Plug-in.

1. Once you download and install it, you should quit all your browsers and other programs, and do a full computer reboot, not just a browser reopen. After your Mac is back up and running, sign in if you have to, then run Disk Utility Permissions Repair to make sure Flash Player gets fully incorporated into all your web browsers that can use it.

2. When Disk Utility is done, close it and go to System Preferences. You'll see the Flash Player icon along the bottom row, under Other.

Click on the Flash Player icon to open Flash Player preferences. Along the top, you'll see 5 tabs. Click on the Storage tab. Under Local Storage Settings, below Learn more about privacy controls, about halfway down the window, there are 3 things to choose. It's best not to choose the first one, which will allow sites to save info on your computer without your knowledge. That can be very dangerous. I have the middle radio button checked. If you choose the 3rd option - Block all sites from storing info... some things such as videos, probably won't work well, if at all.

3. Click on the Camera and Mic tab. Here, I recommend you choose the second option - Block all sites from using the camera and mic. If you don't have a camera or mic on your computer, it won't make any difference. However, if you have one or both connected, someone could hack those and be recording you or anyone near your computer without your knowledge. I've never had this happen, but Flash Player is notorious for being hackable, so just play it safe. I don't have either a camera or a mic connected to my older Mac, but I do on my newer Air. So, I just keep all settings the same for both.

4. Click on the Playback tab. What you choose here is up to you. Personally, I chose Block all sites from using peer-assisted networking. I think it's the safest thing to do. However, if you need it, choose the 1st option.

5. Click on the Updates tab. Choose one of the top two options. I have the middle option chosen, but you might want the first one. I need to say this about Adobe notifications... they tend to come rather late. I read a couple of security blogs regularly, so I usually find out about Flash Player and Mac issues before I get notified by Adobe. I pass along this info to family members who are not so up on what's happening with security issues.

6. Click on the Advanced tab. Honestly, you really don't need to do much on this page. If you want to, look at Browsing Data and Settings where you can Delete All Site Data and Settings and Delete All Audio and Video License Files. I only have the top one checked, because I don't want to delete the audio and video licenses. Also, the Delete All Site Data and Settings option is already being handled by my browsers' settings, but if necessary, you can check it and delete them manually.

Hope that covers it all.

I believe all current versions of Adobe Flash Player that still support OS X 10.6 Snow Leopard are only those versions that support the latest and last version of OS X 10.6 Snow Leopard and that is OS X 10.6.8.

If you wish to stay using Snow Leopard, it would be best, first, to update to the latest version OS X 10.6.8

Combo Update found here.

Mac OS X 10.6.8 Update Combo v1.1

Before doing any major OS X upgrades/updates, it is wise to make a backup of your important data or backup/clone your entire computer system to an externally connected USB or FireWire 800 hard drive first as a precautionary measure against something happening during to upgrade/update process.

Also, this will give you a backup of all of your data if anything should go wrong with your computer in the future.

Once you update, run Software Update in the OS X System Preferences pane a few times to make sure your Mac receives any other updates and securityupdates.

Even after your computer has been updated to OS X 10.6.8, the version of Safari that comes with that version is very old and is no longer supported and at this late date, is considered, now, a security risk.

As has been mentioned, if you update your computer to the OS X 10.6.8 version, it would be best to change web browsers to one that still, currently, supports such a older OS X version like Mozilla Firefox which still supports OS X 10.6.8 Snow Leopard.

Good Luck!