Yeah, it’s for 64-bits, and that CPU is 64-bit capable, so you really should switch to it (32-bit x86 is generally considered legacy at this point), but that’s neither here nor there.
If you were on a compatible system, you would download the appimage to somewhere (we’ll use your home directory, ~/ just for simplicity here), then open a terminal. It should default to your home directory, so no need to change directories, but if you did, you would type ‘cd /whatever/path’ to get there.
Once you’re in the same directory as your appimage, you just type:
chmod +x name-of-program.appimage
and it will make it executable. From then on, you can double-click it or run it from a terminal like this:
./name-of-program.appimage