Frank,

The first stage to finger training begins with teaching your tiel to perch on a stick or dowel. Gently nudge the dowel to the portion of the legs. Repeat this routine until the bird instinctively steps onto the dowel. Next, while the bird is perched on the dowel, offer your finger as a perch in the same manner as you did with the dowel.

As with teaching anything, repetition is the key.