Well...
Since it's your first foray into FL, I'd recommend a few things. See that list on the right? Find a few sounds there and try dragging them onto the list of instruments. Next, right click on the name of the instrument and select "Send To Piano Roll." Use this to change the notes for your melodies and other stuff. Normally you only want one instrument a pattern, and you can make up to 99. I hope you know how to do that. Finally, hit F5. That'll bring up the Playlist window where you can arrange your patterns and make your songs longer.
I hope that helped!
-SolusLunes
PS. Check out my music. You'll be glad you did.