Reaching the training server is a great achievement, as you said, you get to experience human ATC for the first time. On a pilot side, be aware that ATC in the TS are also learning, so they might make some mistakes and also some trolls.
On an ATC side, you can learn more about ATC from the user guide, linked below. There are also a couple of useful tutorials on the official YouTube account of Infinite Flight. Make sure to check them.
If you are really interested in ATC, I highly suggest to apply to IFATC when you meet all the requirements that are listed in the IFATC recruitment topic linked below.
Also, you can make an ATC tracking thread, where pilots in the IFC will come and evaluate your ATC skills. It is also a great way to bond with some members and know more about air traffic controlling. There’s an useful tutorial about it that I also linked below.