How do you move allied units in fire emblem radiant dawn?

Answer 1

I'm assuming that you mean the yellow-colored "Ally" units, and not blue-colored units. (these yellow units were called "Partners" in FE9).

The only way to control their movement is to go up to your commander (generally Micaiah or Ike, but can also be Elincia) and choose the yellow-colored option "Order." From there, just pick a playing style. So, to answer your question: you can't move allied units exactly where you want them, just choose to have them do something specific (like avoid enemies or target a specific area).