wallpaper over fresh joint compound
 

Hi. I recently decided to make a number of 3inch diameter holes in my plaster wall in order to blow in some cellulose insulation. Next we will be wallpapering this wall. I have already used "plaster patch" plaster to fill the holes. And I am now using pre-mixed joint compound (in a tub) to smooth over the repairs. However, I am worried about putting the wallpaper over this stuff. Should I do anything before putting up the wallpaper (sizing or priming for example)? Thanks.

Prime it first.

some wall papers show wall coloration thru the paper, its often a good idea to prime or paint with the color of the wall so you don't have that problem. check your wallpaper manufacturer's instructions to see if they recommend sizing.

It's been years since I wallpapered so I'll ask this question for my own general knowledge purposes but doesn't a plaster wall have to be "sized" - even after it's primed - so that the wallpaper paste (adhesive) has a better surface to bond onto?

The OP said that they coated over the repaired areas with drywall compound.

Use primer, Some paints counteracts the glue, Read the specs on your adhesive.

PS
if I'm not mistaken seizing is what you do to the wall paper not the wall

The primer instructions should give the cure times in additon to the surface dry times. Use the cure times to determine when you can install wallpaper.