To use templates to create an assignment, select CREATE -> " Assignment from Template" and select the template created by the administrator.
Depending on what your administrator has unlocked in the template, you can make some changes. You need to set the start and deadline for the test. The most common additional fields you may need to fill out are that you should choose the PIN code for your test. Then press CREATE.
To add students, select either individual students, a Google group, or a Google Classroom group.
Under teachers, you can, as usual, add more teachers to administer the group.