Once your school's Sumdog account has been Clever integrated your students will be able to use their Clever logins to access Sumdog from their Clever portal.
They can log into their Clever accounts from here on the Clever web site. They would then just need to use their Clever login details or they can scan their Clever badge.
Once they have logged into their Clever portal they will be able to select Sumdog from the list of Clever supported apps.
Here is more information on how your students can log into their Clever accounts.
Note: This will only apply to school who are sharing their data with Sumdog through Clever and have agreed to the Clever integration.