I would like to share the newspaper with another person who can also EDIT the paper

In order to allow someone else edit the newspaper, you must give them your login credentials (email address and password). We recommend not using any personal emails or passwords for this, but something associated with all editors. 

The share feature only allows a preview and will not allow for editing.

If you do give someone your login credentials, please be aware that only one person can be in the project at the same time. Otherwise, whoever saves last will save only what is on their screen overwriting the other person’s work. It is also important that all editors use the same browser, since browsers render text differently and can adjust the way text is shown.