You can also visit our Official Infinite Flight Community forum HERE
Look for the Live > ATC Category, and locate the subject "Infinite Flight ATC Recruiting". There you will find details about what's involved with becoming an Advanced ATC subscriber.
It will help you to have some experience on the ATC Playground server, and a pleasant attitude. Candidates should be knowledgable, and prepared to show self reliance and problem solving under pressure. Being able to react proportionately to situations with accuracy is big. Advanced ATC pilots demand knowledgable and skilled controller who can mimic real world scenarios as seamlessly as possible. This is why only those with appropriate skills and attitude are allowed access.