How to switch to a 64-bit OS?

I have a 32 bit OS but it is 64-bit capable. I tried to switch over, never seen the option to do that and lost everything on my computer. Is there anyway I could do this? Why do I want to do this? Cause I play Minecraft and I would like to use more RAM in it. Yes I know how to, but I want to have better rendering, and I want to use more RAM on the Technic launcher. Unless you guys now how to edit the scripts on Technic too. Like -Xm blah 1024 -M x blah 1024, that kind of stuff.