How old is your home before you decide to cover up the popcorn ceiling?
You need to locate the rafters and situate the seams to correspond to them, butting the edges at the center of the rafter. Also helpful to have a second pair of hands to hold the panel in place while you attach whatever fasciners you are using, screws or nails. I've done it before, liked how it turned out, but had sore shoulders afterwards.
We did this to our ugly popcorn ceiling. We strapped the whole space then attached the pine planks (tongue & groove, cottage board, whatever) to the strapping. Add crown mould for a finished edge. Still looks good 10 years later.
You could just remove the popcorn and paint
Cover it with 1/4" sheet rock, mud and paint it.
We did an old popcorn ceiling with pine strips we bought at Lowes . We gel stained before it went up . Great look . I would do it again . That was the living room . We then did the kitchen . The rooms look more like a cottage .
Not sure about the installation part but we recently did a "tongue in groove", knotty pine ceiling in a white wash. We chose a grey-ish white and in satin. Looks great, we think. Also did the old Douglas Fir floor in a similar colour floor stain and it looks similar but has more of the red/pink tone of the fir coming through. Had to sand the old green paint off first and some of the cracks still have a touch of green. Adds character and matches the furniture.