This option will publish your prototype in your Justinmind account. If you haven't signed in you will be asked to.
If you only have one Justinmind account with just one project, the prototype will be published automatically to that project. Once the publish operation is completed you will se the following dialog:
Click 'View in my account' to open your Justinmind account in the default browser.
If you have access to more than one Justinmind account you will be asked to choose where you want to publish the prototype:
This will happen, for instance, if you are publisher in more than one Justinmind account.
If your Justinmind account contains more than one project you will be asked to choose where you want to publish the prototype, or to create a new one: