Multiple users can access the same project at the same time, changes would get updated automatically.
However, only one user can edit the project at a time and others can view the changes. If you have ‘Edit’ access to the project folder and another user is currently editing a particular project, you can take control by going to the top panel where you will see the name of the team member who is currently editing. Hover the mouse over their name and ‘Take Control’ option will appear. Click on it to start editing.