Tips to install cardboard headliner?

I looped a short piece of wire through the roof support in the middle where the dome light mounts, then tied the other end to a short dowel rod. Get someone to help you get the headliner into the car, raise it up to the roof, and slip the dowel rod through the dome light hole, making sure it spans across the hole so the headliner is suspended up close to the roof.

Allow the rear of the headliner to dip down slightly so you can push it rearward. Using wide putty knives to lift the edge of the windshield gasket, you and your helper carefully tuck the leading front edge of the headliner under the rubber. Shift the headliner around to align the holes for the dome light, coat hanger screws, and seat belt anchor bolts at the roof rail. Remove the wire support and mount the dome light to prevent shifting. Repeat the putty knife technique to slip the headliner under the rear window rubber gasket.

Install the small metal clips along the loose edges at the roof rails, then mount all remaining hardware and trim. Keep in mind how fragile the old headliner is and handle it accordingly.

Nothing to it,
Jerry