How to give a supply teacher permissions to SIMS .net.
Supply teacher on cover needs to take register
How to make supply staff users of the system
User account for cover teacher

If a person has been assigned to Cover in Focus | School | Arrange Cover, then  a prerequisite is that they have been entered in Focus | Person | Manage Classroom Staff.

To give the person access to SIMS .net so that they can mark registers etc, use Focus | System Manager | Manage Users
Change both Active and Role to <Any>, enter part of their name and click on search to ensure that the person is not already on the system as a user.
If they are not, then click on New
Input part of the surname and click on Continue
Their name should appear in the Matched People list.  If the name does not appear, remove part of the Surname and click on Continue again to widen the search.  Do not click on New as this would add a user who not linked to the person with the cover record.
When the person is located, highlight the name and click on Open
On the Groups panel, click Add to add the teacher to the required groups - usually Class Teacher
Change the User-name if necessary
Click Save
Make a note of the Password so that the user can login to SIMS .net