You can change this via Admin > Config > Security Settings.
To make changes to these settings, you'll need the System Admin role. If you don’t have this, you’ll need to ask your team to give you access by following these instructions: How do I add a user role to a staff member?
Click on the padlock icon.
Here you will see the following:
Select the desired time limit via the hour (H) and minute (M) dropdown boxes and click Save, this will adjust the amount of time your ScholarPack stays open for all users on your site before they are automatically logged out.