It should be added automatically if you have referenced it. You can add any file you want to the deployment package manually though. I would suggest you try that.

1. Right-click on your project in the "Solution Explorer" window and select "Properties".
2. On the "Application" tab, select the ellipses next to the "Miscellaneous Files" property under "Deployment".
3. On the "Deployment Files Editor" window click the "Add" button.
4. Browse to the file from the "File" property and click "Ok".

Now when you deploy, this file should appear inside your deployment package.