When it comes to making music if you’ve got a Mac then GarageBand should come installed on it - this is one of the easiest music packages I’ve ever come across. On Windows I’d rather not recommend a specific music package as there thousands of them, including many great free ones. Googling around should help you find one that suits you.
When it comes to pre-made music you might want to check out Incompetech (http://incompetech.com/m/c/royalty-free) first. It’s the site of one musician, Kevin McLeod, who has produced an absolutely huge archive of free music he’s composed across all genres for people to use for free. What a guy. If you want a wider choice then check out Indie Game Music (http://www.indiegamemusic.com) which has free and paid-for music from a ton of people.