Many crypto exchange still offer trading pair crypto with stable coin of USDT, and USDT still has the highest trading volume and market cap compared others stable coin. To trade USDT with others crypto is not need to create the personal wallet, and if you want to hold any crypto in personal wallet is better hold Bitcoin because this coin has more potential to offer big profit in the long run.
You can't really "use" it, it is just for trading on the exchanges so you know how much dollars you have but it works for nothing else. I have always hated tether and I would suggest you to not use them for now anyway. However if you really want to than you can go to any exchange that has tether and just pick it up with your money, than you can start to trade it with any coin they provide to the tether pair.
Usually they allow you to trade big coins like bitcoin and ethereum and what not. I would honestly prefer to trade bnb at binance for other coins instead of using tether. At least that one has a purpose and a reason to exist, help you get your trading fee half down instead of paying the full price for it. Tether doesn't have that and it is used nowhere and worth nothing.