If you can't find the search box (likely because it's been disabled) or you have another version of Windows, i.e. WIndows 7 or earlier, followthis guideto determine whether you're running a 32 or 64-bit.
On the right hand-side look for System Type. If the System Type value includes "x86" in it, you will be running 32-bit. If the System Type value includes "x64" in it, then you're running a 64-bit.