When creating a request for an outgoing payment you can enter the bank accounts to which the payment should be made. You can check "Save for group" and add a description so that the other group members can also use these bank details when creating outgoing payments.
You can also save your own bank details in your user account. Click on your name in the upper right corner and then on the button "Create bank account". Fill in all the fields and finally click on "Save bank account". After saving your account, you can click on the gear icon and define in which groups the bank account should be visible. This will allow other group members to easily select the bank account when creating outgoing payments.
You can find the bank accounts that are associated with your group under the "create payment" panel. Here the group admins or the bank account owners can add a description to each bank account or delete the bank accounts from the group.