Read more about different types of users here: User types on Solverboard
As you scale your team, you may need to increase or decrease the number of Solver or Professional seats available.
To do this, head to Settings in the left hand menu:
Then click Manage users.
Simply follow the link to either add more Professional users or more Solver users.
(In some cases, it might be better to upgrade to a higher Solverboard package which includes more seats along with other great benefits).