Basically, you should have a track that mounts on the top of the door frame, a guide that mounts on the floor, and some rollers that mount on the top of the door and hang in the upper track. I can't tell you how those rollers are attached to the door because they're all different. Most likely, they just screw in, so there would be two roller assemblies and a bag full of screws. As to how the rollers fit into the track, that also varies depending on the door - but usually, the rollers attach to the door first and then you hang the whole thing on the rollers. (Gravity keeps it in place.) But sometimes the roller and track are all one piece that is first attached to the door and then screwed into the door frame.
Other parts: The track should have a stopper at the end which may or may not be attached.
Give us a list of the parts you have - and try to describe them.