To run NASM:
Start > Run > 'cmd' ENTER
'nasm <command line arguments>' ENTER
Any particular problem you're having?
Edit: I do believe there is a NASM IDE being developed, as part of the new NASM packages. Somebody on this forum is doing it too, but I can't remember their name. My solution also requires your NASM to be in the PATH, which it probably won't be. Try also doing this:
'cd <path to nasm/source files/etc' ENTER