Assign user to project
Navigate to the home page and select a project where you want to assign the user.
Now, Go to "Settings" -> "Project Settings" and click on "Manage project" like shown in the image below.
From the "Add Existing User" dropdown menu, select a user. The user will get assigned to the project.
The user will get added.
Once you're done with your changes. Click on Save Project (Draft).
Changes are now saved locally, in order to save these changes on the app. Click on Save.