HighSide requires a user with administrator privileges to deploy the application to your Microsoft Teams tenant. The administrator user will need to have access to the MS Teams Web Admin Portal which can be accessed here - admin.teams.microsoft.com.
Navigate to the Microsoft Teams Administrator Web Portal (admin.teams.microsoft.com) and open the “Manage Apps” section (This will be under the “Teams Apps” tab on the left hand side of the Admin Portal.
In the top right search bar, search for “HighSide”
Once the app comes up you will see a “Permissions” tab in the table. Click “View Details”.
Click "Permissions" and then “Review Permissions”
The Admin portal will ask you to sign in to verify your information. Once you’ve re-authenticated, Microsoft Teams will allow you to grant the permissions for SecureTeams.
Congratulations, you are now ready to begin adding SecureTeams to conversations and tabs within your Microsoft Teams tenant. Do get started with this, simply follow the guide here.