To access Friendship Shop, press Gifts at the bottom of the main game screen:
Then click the Send button:
And click Merchant in the Send gifts menu:
You can also select the Friendship Shop tab when you open any other Shop:
Here you can spend Friendship Chips to purchase hero equipment and Soul Stones of Faceless and Cornelius.
New goods appear every 24 hours at 9:00 PM your in-game timezone. Also, you can refresh the Shop with emeralds.