Open the web browser
In the upper left corner there is a folder (bookmark) with your school's name. Click on that folder.
Click on the Vklass link
Choose "Logga in med Göteborgs Stad"
Sign in with your school account - username and password
Go to https://auth.vklass.se/ or open the mobile app
Choose organisation "Göteborgs Stad UBF"
Choose "Logga in med Göteborgs Stad"
Sign in with your school account - username and password
.... and sign in with your school account.