You can add additional users to Float using the following steps.
1. Select the 'Number of users' option on your dashboard followed by 'Manage users'
2. Select 'Invite a user to ...'
3. Enter the first name, last name and email address of the person you would like to invite
4. Click add user to send the invite
The new user will then be sent an email invitation to access Float, all done. If you're looking to remove a user find out how here.