There are multiple possibilities for you to be involved in the roster planning as an employee. In addition to adding your availabilities and applying for shifts, an admin can also give you the right to assign yourself to existing shifts.
You are generally able to apply for shifts with the employee role.
This is how to apply for a shift as an employee:
Log in with your employee profile.
Click on the calendar.
Click on a shift that you would like to work.
If the shift turns yellow, your application has been successful.
Your admin will now be able to see that you have applied for that particular shift. They can then decide whether they will assign you to the shift or not.
Watch this video in which Mevlona explains applying to shifts in more detail:
If you have the "Self-assignment" right from an admin, you can independently assign yourself to shifts that an admin has created.
The process is the same as applying for a shift but in this case, the shift will turn green as you have already assigned yourself. It looks just the same as when an admin assigns you to a shift.