Do a DATUM AXIS>THRU CYL and pick on the hole's cylinder. This creates a datum axis to use as a host for the datum reference frame. Although the hole already has an axis, it is good practice to greate a new one.
Do a SETUP>GEOMTOL>SET DATUM and select the datum axis picked above. A dialog window will ask you for a name for the datum and ask you if you want to make the datum reference frame free or imbedded in a dimension (e.g. the cylinder's diameter). Pick one.