In the top right corner of your Authorea document, you will see a Share link next to the open lock. Clicking this brings up a window with a few options:
Add collaborator: In this field, you can type someone’s email address to add them, or search for them in the Authorea community. Once you’ve selected them, click the red plus to add them as a collaborator. You can also invite authors from your Gmail address book.
Get Shareable Link: Clicking this button will create a link that will allow you to publicly share your work - anyone with the link will be able to access your Authorea document.
Privacy: Here you can change your document to be Public (anyone with the link can access it to comment or share) or Private (only you and your coauthors can see it).
Social Media: Quickly share your Authorea document on Facebook, Twitter or forward it in email.