New to Java

Hi, I am new here and just finished AP Computer Science learning Java. I am now doing a little programming project for my brother. He is giving me a folder with spreadsheets. I should be able to detect if he has added new spreadsheets. I have figured out the logic of the program (except how to detect if he adds new spreadsheets). I found some sample code using Apache POI, but I wasn't able to use it because I kept getting compile-time errors saying the POI or HSSF libraries or whatever couldn't be found. So I went to the Apache site to download what ever I needed and had three issues:

1. I didn't know what to download
2. Even if I wanted to download something, they weren't all in one zip or rar file so i didnt't know what to download or how to do it
3. I don't know where to put these files so I would be able to run my program which I am crrently just compiling and executing from a .java file

I know this is a lot, but thank you very much in advance.