I have done this a couple of times by fitting the back, along the rear window, then fitting the front. I then position the metal braces in a way that they seem spaced correctly. Before any of this I opened up the "toothed" strips a bit to allow more room. Once everything is in place I used a rubber mallet--gently--to tap it back down into place.
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Tim--'72 ES, '90 240

A helper and a lot of patience! I think the perforated headliner, with the plastic outer frame is the easiest and my 1960 grey fabric, with no frame is the hardest. I also found that some aftermarket head liners are not 100% accurate, which added to my frustration. Make sure the metal stringers are in the exact position as when you removed them. The service manual suggests you start from the back frame, working forward to the front window, stretching as you progress from one stringer to the next. Use a plastic or wooden spatula to force the edges onto the toothed frame, careful not to rip the material. If this sounds too difficult, then another option is to have a professional do the job for you.
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Cam a.k.a. CVOLVO.COM