Help with Door Glass Track Installation

The car had no door panels so I can see all that is in there. Also, Murray, it does not have the felt liner; that is something I had best look into later. I am just unsure as to how to get the bolt into the top, which is the red end, as the other side's channel is present and I tried to remove it but could not get any tool in there to remove the bolt. I'll have to keep at it and I'll let you know what happens. Thank you all for your responses; they were all quite helpful.