You can invite users to be a part of your team.

To add new users, click on settings from the top menu. 

From the options, select User Management, enter the Name, Email, and Access level of the user you want to invite and click on Add User

Once you click on Add User, an invitation email will be sent to the specified email address

Once the user accepts the invite , the User Status will change from Invited to Accepted, however you can start assigning leads to the user even before the invite is accepted.