Well first of all you need to become a TL1, so you need to check the requirements for becoming a IFATC they will be below. Once you pass your written exam you can use training from a IFATC Trainer, this will be linked below as well. Finally you can use a ATC tracking thread to practice for the practical exam, for the written exam you just need to know your stuff, use paper and take your time. Here are the links: