If you want to be become a Mobile application Tester then you can do a the Appium Automation Training Course which is available online as well as through classes.
Let me tell you few things about Appium. It supports Mobile Application testing on Native, Hybrid and WebApps for Iphone, Ipads & Android real device and Emulators/Simulators whereas Selendroid supports Mobile application testing on Native, Hybrid and WebApps for Android real device and Emulators only.
Now it is your choice whether you want to go for IPhone or Android based technology.
Appium training tutorials are easily available in the market that will help you in learning Mobile apps automation testing for IOS. https://market.edugorilla.com/
You can also watch video lectures in which you will see the entire coding part done step by step. Various good tutorials explain the whole technology in detailed and practical approach.