Setting your PIN for your debit card is done when you activate your card.
If you need to update your PIN at any time, please take the following steps:
After logging in to your account, tap "Checking"
Tap the gear icon in the upper right corner
Tap "Update Card PIN"
Note: It will ask you to Enter your PIN, this means entering a completely new PIN. You will not be asked for the previous PIN.
Please keep in mind that it can take up to 12am Central Time for the new PIN to be set.