Start in the middle and work toward the sides and ends. There should be some "nailing" strips of cardboard (maybe plastic or other material to hold nails {older models} or staples) or fingers to hold the sides and ends of the headliner in place. The "nailing strips" might have been removed if damaged or they were in the way of body work. They are typically held in place with fingers or tabs.
Once installed the wrinkles can be removed by light heating for vinyl or steam for fabric. Just take it slow and easy and it will work out. Putting in a headliner in a '57 Nomad with my wife was nearly fatal for our marriage. Luckily both were saved.
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How Sweet the roar of a Chevy four!