What is this in english please: ma sœur et moi nous sommes amusés à nager dans les piscines.

Comment on fait pour employer les auxiliaires êtres et avoirs

So i need to have this packet done by tomorrow at like 9: 45 am

How do you write i/he/she went to *blank location* in past tense in french? like. how do i say something like i went outside yesterday, or my friend went to the store yesterday? i really want to understand this, but none of the websites i use are really doing a good job at explaining it