No, you can't "upgrade" from 32-bit Windows to 64-bit Windows. Essentially, it's a complete reinstall.
Things to consider:
-- 32-bit Windows requires less resources to run than 64-bit Windows (IIRC, minimum RAM is 1GB for 32-bit vs. 2GB for 64-bit; both technically recommend that you have 4GB of RAM)
-- 32-bit Windows is limited to a maximum of 4GB of RAM; 64-bit Windows can access a whole lot more, depending on the version -- Windows 10 Home, for example, can have a maximum of 128GB of RAM, while Windows 10 Pro/Enterprise/Education can have a maximum of 2TB of RAM (although you're primarily going to see that with server-grade motherboards, as most consumer motherboards top out at 64GB anyway)
-- 32-bit Windows is going to limit the applications that you can use. It's not as critical if you're not planning on playing games, but a lot of the newer games are specifying a 64-bit Windows (mainly because a) they use DirectX 12 or b) they require at least 8GB of RAM to run).