String partial = ("SELECT c FROM content AS c WHERE c.artist LIKE \"%" + like + "%\"");

Is there any one that can explain the proceedure to get this query introduced into the persistence unit so it can be run?

I haven't actually used SQL with Java before, but there are plenty of tutorials / examples out there in the world wide web. This link might be a good place to start since you are using MySQL. Good luck :)

I looked at that link and It might not address MySQL and the netbeans.
It looks like a helpful site though.