If you get scheduled on a day when you can't work, you can help your manager find a replacement.
To make your shift available for others to pick up, click on the shift to open the details. Then, click on the options menu (3 dots) at the bottom and select Make shift available.
This allows anyone who shares your position and location to see the available shift and apply for it. Keep in mind, you are still responsible for the shift if it's not picked up and/or approved.