Have you registered your copy of Trainz? There are no icons appearing at the top of your message so we cannot see which version you are using. Registering also makes it more likely that others will help you.
Normally all you need to do is attach the road to both sides of the crossing and the track to each end of the crossing. Now I believe that TS12 (the initial unpatched release) did have a problem with cars not stopping at the crossing but I believe this may have been fixed in the patched version.