How can employee add additional bank account themselves

Good afternoon, @Liz227. 

It's great to see a new face here in the Community.

First, you'll want to invite your employee to enter and view their information in Workforce. 

Once they accept the invite, they'll be able to perform the steps below to enter bank details and more: 

1. Select Get set up or Complete setup now (or Sign in).
2. Fill in all info: personal, W-4, and bank account. Bank account only appears if your employer has selected to pay via direct deposit.
3. Check all of your info to make sure it's correct and sign your W-4.
4. Tap Save or Submit.

I hope this helps. If you have any other questions, don't hesitate to ask. Have a wonderful day!