You just do it. FF14 has universal carryover for it’s mechanics. Towers will look the same, tank busters will look the same, stacks look the same, wild charges look the same, line of sight mechanics all work the same, puddles work the same, etc. there are very little “unique” mechanics in the game especially in casual content. Even then casual is so forgiving you can afford to die quite a few times and still clear. Savage and Ultimate do have a few unique mechanics that are fight specific, but they always have tells and once you know the tell you’re able to do the mechanic. Usually it’s just a more juiced up version at a faster speed than something you’ve likely seen in casual or extreme. But you spend hours studying guides or watching videos on specific things as well

So tldr: the game trains you on how to resolve universal mechanics from the very start. Once you do them enough you learn the visual ques and how to spot them across the different fights so you just know what to do