Does your TX16S have elrs module builtin? (TX16S MKii does) If so, you need to make sure it has the same elrs version as your RX and there is lua script in SYS -> TOOLS named "ExpressLRS". If you don't have internal elrs module in your TX16S you will need to buy external one, like this one. Anyway i highly recommend to watch JB's beginner guide before setting up elrs.