Here's how to determine which meaning it has in a sentence:
* "You saw": If the sentence is talking about something that was observed. For example: "Viste la película?" (Did you see the movie?)
* "You wore": If the sentence is talking about clothing. For example: "Viste un vestido bonito ayer." (You wore a beautiful dress yesterday.)
It's important to consider the context of the sentence to understand the correct meaning of "viste".