It's a huge pain. I hooked two lengths of string to a piece of wire and fed them from the closest opening in the frame to the hinge bolt holes. Each piece of string was tied to a hole in the insert and then I wiggled the insert through the channel to where they aligned with the hinge holes. That was the easy part, getting the bolts started in the inserts was the real challenge.
Two tips....run a tap through the inserts before you start, using plenty of PB Blaster when you do it...and have some overlength bolts handy to to catch the insert or hold it in place while you start your Torx bolts. I used some 2" bolts with a nut threaded most of the way up the bolt. This let me go in through the hinges and catch a couple of threads, then I could turn the nut down and pull the insert up tight against the frame so I could start a Torx.