To upgrade the licenses, follow the instructions below.
Login in AppExchange (https://appexchange.salesforce.com/);
Go to My Installs & subscription under your photo menu;
Find Tuvis App and click on "Manage Subscription";
So, select edit (1) then adjust the number of users (2);
It will be requested some complementary payment data. Once fulfilled, just confirm;
Send an email to [email protected] to inform us about the purchase so we can upgrade the licenses.