To get them to use the coop, you need to 'home' them to it. Shut them in for a few days, then let them out to the rest of the run.
As for why they aren't laying, could be a number of things. How big is your tractor and coop? Overcrowding stress can factor into how productive birds are. How long have you had them? Moving to a new environment can be very stressful and cause them to stop laying. What are you feeding? Could be that they just aren't quite mature enough to be laying.
It should be noted that since you do have a rooster, layer feed should not be fed to your flock. Layer feed is for ACTIVELY laying birds only. The high calcium content can be fatal to birds that aren't using it up for egg production.