Thank Goodness You're Here!

At the start of the game, to the west of the main square you'll find Nick trying to raise his store shutters.
Slap him several times to raise the shutters and reveal Nick's Bricks.

Now whenever you visit the main square slap the wall of Nick's Bricks.

After you gather the birds for the bean man, you'll end up at the bar. Leave the bar, head to Nick's Bricks and smack the wall until it finally creates a shop.