Depending on the plan you're on there will be a limit to the number of people you can add. If you need to add more people, its easy to change plans.
Having multiple team members allows you to assign and track feedback through workflows and also give your team access to projects they are working on and restrict them from projects they're not.
To invite your team, click the People menu from the top right.
Followed by Invite People
Type in the email addresses of your team or clients that you would like to invite to your Userback account. To add a team member manually, click the Create new user manually link.
Once the user accepts the invitation, they will be ready to collaborate and start working on feedback for the projects they are assigned to.