Getting from OSX 10.9.5 to High Sierra?

Make sure you back it up.

Check your applications to make sure they will be compatible with High Sierra. http://roaringapps.com is a good resource.

Once you have confirmed you have a good backup, open the Mac App Store. Find High Sierra in the store, and click the button to download and install it.

Sewil26 wrote:

I tried to install after backing up. Message from High Sierra "can not be installed on this computer"

Then either your computer is too old to support High Sierra, or it does not meet the minimum requirements (free disk space most likely).

What year/model is your computer?

macOS High Sierra - Technical Specifications

Your Mac isn't compatible with it. If desired, back up your data,check your applications for compatibility, click here, and download El Capitan from the Mac App Store.

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Back up your data,check your applications for compatibility, and download it from the Mac App Store.

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So what model of Mac are you attempting to install High Sierra on?