As I know Xamarin is there to create mobile apps right? If you are creating mobile apps and using them to connect and share data between the server, you have do some back-end stuff. (Only PHP and MYSQL allowed here as programming language and database application, respectively).
If you need to connect to the MYSQL server remotely, you are not allowed to do it in free platform. Please consider our premium-grade plans.
If you have further more questions, feel free to reply here