take it to a auto interior shop  

(where required) Good spray adhesive 3M spray 77 or spray 80 NO EXCEPTIONS. Follow directions EXACTLY !!

spray light coat to both mating parts... allow to dry. When ready to assemble spray light coat on 1 part... allow to tack up then assemble.

If the directions are deviated from... short term hold is generally OK but long term hold will fail. If followed exactly short term hold is amazing allowing you to easily "tension" the headliner and eliminate sags and wrinkles and long term hold is permanent.

Gary

I did my own on my Trans Am at age 17 and now I am 39 and its still holding, not bubling some years later. Use the 3M stuff spray as Fake68 said, take your time. I did it by myself but a second hand is always usefull. Avoid alcohol. Take your time. A nice warm day with clean floor helps. I saw my old car recently and its still holding, prob hold longer than the original. I know NOS sells the correct spray glue and headliners.
If you lack patience. Pay someone to do it. Hardest part is re installing in car. Pain in the butt. If I can do mine at 17 and last all these years I am very confident anyone else can. I seen peopel rush and chinse out on glue and then it sags, bubbles and falls down shortly after. Best of luck