Volvo trucks VNL 760 and 860 us the same door window part. It's actually the same as 2017 models.

Not a professional method but this is what I found worked for me

After disassembling the door and removing rubber remove the rear vertical glass rail inside the door (right for passenger door or left for driver door). It's just 2 bolts.

Put the new window angled about 90 degree front first and turn 90 degrees back into its normal position (you don't have to insert it into the remaining rail yet). If the horizontal rail and rollers holding the glass - you can move glass up or down to clear space.

Disconnect the bolts holding the horizontal arm inside the door and this will loose one of the rollers. Insert the rear roller first and find a position where you can insert the second roller as your window still can be tilted.

take the 4 black shirt nuts holding the rectangular large silver plate on the front (with door latch and other cables ). . This would help to put on the front roller.