Desktop: To add a joint account holder, log in to OnCommand and choose “Tools & Services.” Under the “Other Services” section choose “Add Joint Account Owner to Bank Account.” Fill out the required fields and click “Submit.” Mobile: Log in to your First Command mobile app and tap the menu icon at the top right corner. Choose “Tools & Services,” then “Other Services.” Next, choose “Add Joint Account Owner to Bank Account.” Fill out the required fields and tap “Submit.”