If you have a Centerfire kit, those parts are most likely for the Fire Control Group.
The spacer goes on the right side of the disconnector (looking down the rifle as if you're ready to shoot). The spacer keeps the disconnector from sliding side to side in the trigger.
The sleeve goes through the trigger, disconnector and spacer to make assembly easier. The trigger pin just slides through the sleeve once the FCG is in place.
Since you will most likely be replacing the FCG with U.S. made parts to meet the 922(r) compliance, the spacer will no longer be needed. That is assuming you use decent U.S. parts (i.e. Tapco G2, Red Star Arms, or FSE). If you use the crap Century stuff, the spacer may still be needed. The semi-auto FCG included with the kit by Centerfire is not a U.S. made set.