Wall sound proofing - hanging rows of sound proof "curtains"
Sound isolation foam doesn't work like that. It's designed to remove reverb, not block sounds. What you want are "soundproof curtains". These are designed to be heavy curtains that can actually block sound. Basically anything else with mass will have similar effects, but these are a good way to block off the entire wall. You mount them the same way you would mount regular curtains, though with more attention paid to weight. If you have a bunch of books, sticking your bookcases against that wall would also help.

Doing this correctly basically involves opening up the wall and decoupling your apartment from your neighbor's. I'll assume that isn't an option.