Updating my Computer

If running Yosemite, the Mac can at least update to 10.11 El Capitan.

See here: How to upgrade to OS X El Capitan - Apple Support

Depending on the exact model, it may or may not be be able to update to 10.12, 10.13, 1014 or 10.15.

See

here: How to upgrade to macOS Sierra - Apple Support

here: How to upgrade to macOS High Sierra - Apple Support

here: How to upgrade to macOS Mojave - Apple Support

and here: How to upgrade to macOS Catalina - Apple Support

PurePerfection wrote:

the year is 2012

In that case, it can update all the way to macOS 10.15 Catalina.

Follow the steps in the link provided above for Catalina.

Do read here before you update however: 32-bit app compatibility with macOS High Sierra 10.13.4 and later - Apple Support

PurePerfection wrote:

the year is 2012

Thanks. See Phil's post. You will probably have to upgrade to El Capitan first before you can upgrade to Mojave or Catalina. Older 32bit apps will not run in Catalina so you will either have to upgrade them or install Mojave.

What year is your iMac?