I had the same situation so this is how I did mine:
Placed bows in roof sections swapping them until I found which bow length was best where it sat.
Labeled said bows in order from front to rear.
Slid the bows inside the headliner and installed including the two rear spring tension rods that attach to the rear most bow.
With rear glass and windshield out of the car, cemented these sections in place by folding the material over the gasket lip and held in place with multiple spring clamps until dry. Trim as needed for glass gasket install.
Did the same along the sides starting from the front and moving rearward. This part was a two person job but I suppose it could be done alone if it had to be by alternating from side to side.
When all was dry in place, removed spring clamps and installed window/gasket trim.
It can be a bit of a challenge and took some time and patience but came out great.