Good for you Rosalie!
So happy to hear that you are thinking in terms of finishing techniques, such as blocking! It is so important that we don't skip this important step. Acyrlic doesn't exactly "block" like wools and wool blends...but I can say from experience, that your finished stitches will have a nicer, more even appearance after blocking! Much nicer.
And the other knitters gave good tips on how to block.
I usually just pin the garment down onto a blocking board, then lay damp white wash cloths or towels over the top of the pieces, and leave everything alone til the towels are bone dry. The towels kinda steam the pieces gently, and without heat.
Patience, patience, patience. Let things stay put til BONE DRY.
In the meantime, start another project, keep yourself occupied...and you won't jump the gun and un-pin your pieces too soon!
Be sure and post photos of your sweater!!