How to transfer information from an old IMac to a new IMac?

Please read:

https://support.apple.com/en-us/HT204350

Migration Assistant is a program provided by Apple for for transferring your files. It is very easy to use. Basically, the process is as follows.

• You first begin by starting the process of setting up your new computer. You will be asked if you wish to transfer files. Respond YES and follow the instructions you will be given.
• You will be told to turn both computers on and activate Migration Assistant in the old computer.
• The computers should be connected with a USB cable to facilitate the transfer. Wi-Fi is simply not suited for a transfer of so much date and corruption often results. Do not use it.
• You will b given several options as to what to transfer. You will likely want to transfer your settings and preferences.
• You can transfer all or none of your files. You do not have an option to select certain files to transfer. If you wish to do that, then do so manually.
• The old computer's operating system will not be transferred.
• Allow for up to an hour for the transfer process to complete once you start it.
• Enjoy your new Mac.

I hope this is helpful. Good luck.

When you buy a new Mac the easiest, quickest and most reliable method to migrate from the old Mac to the new Mac is to simply connect the old Mac's Time Machine External Hard Disk to the new Mac using a USB cable before you turn on the new Mac. You will likely need a USB A to USB C adapter, you can find them on Amazon for $10 or less. When you start the new Mac for the first time it will startup Setup Assistant (SA), SA will get to a point where it asks if you are migrating from another computer, select Yes  and follow the on-screen prompts and it's done! It is THAT simple.

If you have already done SA on the new computer then simply connect the Time Machine External Hard Disk using a USB cable and launch Migration Assistant (MA) which is located in Applications - Utilities - MA. Then follow the on-screen prompts. 

The ONLY difference between MA and SA is MA will create a new user account that you need to log into.

Both SA and MA migrate applications (not 32 bit apps), data files & settings. They do not migrate Mac OS itself. Some professional apps such as Adobe and Microsoft apps may require re-installing their apps as they will not allow them to be migrated. As long as you kept the security keys for installing their apps, it is not an issue. 

Finally, please NEVER EVER use WI-FI to migrate, this will fail in almost 100% of the situations in my experience. WI-FI was never intended to move large amounts of data at one time.

Great. now you tell me after I migrated via wi fi. now I have a sign in screen that asks for password, but neither the old or new one work. I tried rebooting in recovery mode, but command + r or R don't work to start recovery mode. Help?