If one of your indicators is a small one with a dovetail mount that is what you use to tram in the head. There should be a stem mount included with the indicator. The dovetail portion of the stem is fastened to the indicator body and the stem will go into the spindle of the mill held in with a chuck or collet. The probe of the indicator is then swept around the bed by rotating the spindle by hand. The column is adjusted until the indicator dial nulls out. The process is made easier if you put a couple of matched 1-2-3 blocks (without holes) on the bed and ride the indicator probe over the blocks.