It can be done any time after we have received the ASN record. It can be done either from the Vehicle Locator using the Set Priority Level option or it can be done from the Vehicle Details window using the Priority Item (No/Yes/Hot) radio buttons.

There is no easy mechanism for putting a multiple leg move on hold. The easiest way to do this is to merge the Legs back together (can be done from the Legs tab of the Vehicle Details window) and then apply the hold.