You can invite a member to your account from 
Settings > User Management or even while you are adding host to your event.
Add members from User Management page
To add a new member to your account, follow the steps below:
and click on Add User
A popup will appear, for you to add the email of new member and to select the role.
You can also add multiple members at once by clicking on "Add another" button.
Once you've included all new users that you'd like to invite:
click on the "Send Invite" button
The member will receive the invite to Join iClosed on their email, and all they need to do is to click on the "Join" button to accept the invite, continue with the sign up process and start using iClosed.
Bear in mind that the invite link expires after 7 days, and in case invitee didn't accept the invite within that period of time, you'd need to re-invite him from the 
Settings → User Management page.
You can add team members for free while you are on free trial, but you will be charged for the total number of members according to your plan after your free trial ends/subscription starts.
Learn more
Add members while adding hosts to your event
We've made it easier for you to invite users while you are creating an Event and setting up Hosts.
You can quickly invite them by clicking on the "+Invite Users" button at the bottom left of the hosts section
A popup will appear, for you to add the email of new member and to select the role.
You can also add multiple members at once by clicking on "Add another" button.
Once you've finished adding users, click on the "Send Invite" button. As soon as the invites are sent out to your users, you will see them as Hosts in the Event setup, and you will see "Pending Invitation" badges (see image above) for such users.
You will be able to select such hosts and to include them in the Event setup immediately, but they will be able to start getting calls only once they:
have accepted the invite and logged into account and
they've set their Availability.