So how do you buy things with bitcoin

So ok everybody says don’t sell bitcoin and to hold it. Alright I get that. Let that thing go sky high. But out of curiosity how would you use bitcoin or any crypto to buy things. Do you need like an app where you can use your phone as a card and it’ll convert bitcoin to the amount you need to pay for stuff.

I’m a complete noobie so if I sound dumb in the subject it’s because I am.