Learn Spanish (Latin America): Ella sabe nadar muy bien.

In Spanish, we use the verb saber to talk about knowing how to do a skill, like swimming. Conocer is used for being familiar with a person, place, or thing.

Where are the words for 'how to' in this sentence?

In English, we say 'She knows how to swim', but Spanish is simpler here! When you use saber right before an action verb (like nadar), it automatically translates as knowing how to do that action. You don't need to add an extra word for 'how'.

Why does nadar keep its -ar ending instead of being conjugated?

When two verbs are combined to express one idea, only the first verb is conjugated. Because sabe is already conjugated to match ella (she), the second verb (nadar) must stay in its infinitive (dictionary) form.

Could I say muy bueno instead of muy bien?

No, because bien means 'well' and bueno means 'good'. Just like in English, we use 'well' (bien) to describe how an action is done, like swimming. You would use bueno to describe a thing or a person instead.