How do you know when to use です or います？and when to use the particles は or の？

I'm only a beginner learner in Japanese, and I'm having trouble on when to use です or います.

I also have trouble on when to use は or の.

Example:

まゆさん は ともだち ふたり が います。

Why would it be は instead of の, and why did they use います?

How do you know when to use each particle?