David,
In short, you create an assembly and then insert components into the assembly. Components are placed using constraints such as Insert, Mate and Align. If you select the cylindrical surface of a hole and then of the fastener, an Insert constraint will automatically be created. You would then add a second constraint by selecting the bottom of the fastener head and the surface it will mate against. You could use the Repeat function to easily place multiple fasteners.
For more in-depth instruction, I would suggest you go to www.ptc.com/go/first and in the Training and Resources tab, you will find FIRST specific curriculum as well as links to our basic Academic Program training materials.
Hope this helps.
Adam