Help! My Mac won't let me open BookCreative. What do I do?

No worries; this is due to your security settings. It used to be that you could simply go into your Gatekeeper and select System Preferences > Security & Privacy > General, set Allow apps downloaded fromAnywhere:

But in Sierra, this option has been removed. Luckily, there is a simple workaround:

  1. After downloading an app from an unidentified developer, drag it to the Applications folder.

  2. Select the app and right or control-click.

  3. Click on Open.

  4. Click on Open again to confirm you want to complete the action.

 

If you are getting a /private/var/folders message:

 This means that your app isn't readable in its current location. Move the application from the /private/var/folders... directory to your Documents or Desktop folder.