Outland Shop becomes available at team level 25. You can find it by tapping the Shop button in the upper-left corner of the Outland screen:
You can also select the Outland Shop tab when you open Merchant on the main game screen:
Here you can spend Outland Coins to purchase Skin Shop Certificates, Skin Stone Chests, hero equipment, and Soul Stones of Luther, Jorgen, Elmir, and Qing Mao.
All goods are updated every 24 hours at 9:00 PM your in-game time. You can also refresh the Outland Shop using emeralds.