If you need a coworker to help you finish a form, you can @mention them on the form.
Mention a coworker on a form
Create the form (see Adding and completing a form on mobile). Now you have edit control of that form, which means you're the only one who can edit it right now.
Open the Notes tab of the form, located in the right-hand panel.
In the note field, type @, then type the first or last name(s) of the worker(s) you need to help you finish the form. Make sure whoever you @mention has access to this form.
Tap Save, then the worker(s) will be notified and given a link to the form on web. They'll need to take edit control on web to edit the form on mobile.
To @mention another worker after you've saved the note, just start over from step 3. Notes are NOT saved when someone finishes the form.
Contribute to a form from your coworker
Once you've taken edit control of a form on web, you can edit it on mobile. You can continue to fill it out, finish it, or tap Release Edit Control to send it back to the form creator.
You can see forms you've taken by tapping the To Do button on the left side of the screen, in the Forms I've Taken tab.