There are multipe ways to get to the withdrawal flow:
a.) Via the wallets screen
Step 1: Tap the wallets icon in the footer or the wallets row in the watch list.
Step 2: Tap the withdraw button underneath the list of your wallets.
b.) Via the wallet for an individual coin
Tap the wallet button in the quote detail section ...
... and then ...
... or the wallet amount on the wallets screen.
Step 2: Tap the withdraw button.