End-users cannot access TinQwise Control, but Admins can. Therefore, an Admin can promote a user to an Admin, here's how.
Go to TinQwise Control, click on 'Users'
From the user drop-down, select "View details"
From the hamburger menu on the top right, select "Promote to admin"
Now you can share 'yourplatform.platform.co.nl/control' URL to the user you promoted to an Admin.