How can I assign multiple users to Client Portal?

To assign more than one user to a portal, the best thing to do is set up a password protected portal instead of adding a new user the traditional way. 

1

From your WordPress dashboard, navigate to Projects -> All Projects.

2

Select the portal you want to assign multiple users to.

3

Under Publish -> Visibility, click Password Protected and enter a password to share with your users. 

4

Now simply share the URL for your portal and the password with as many different people as you like! (They won't need an email address to log in)