Follow the below steps to add collaborator:
1. Click on your Account profile from the Top-Right Corner and select "Organization Management" drop the drop-down menu
3. Add e-mail ID under "Collaborator Email" with whom you would like to add as a collaborator
4. You can also select the specific permission "Authoring(edit)" and "Viewing(read-only)" for the collaborator by clicking on the Options dropdown.
5. An invite email will be sent to the Collaborator Email with login information.