Take a look at this section
of the official samba howto. If it seems a little over your head just back up a few sections and play around with smb.conf.
There's a lot of configuration options for samba, but you'll probably only need a small subset of those options. Play with it long enough and occationally reference the docs and you should be able to get it. I have a little bit of experience with this myself as, I'm sure, several other people around here do, so if you run into some specific trouble let us know.