What is the legal age to start working in massachusett?

I just turned 16 on July 1st and I was wondering if I was able to legally work or do I need to get a working permit? I heard that it depends on where you work and I was thinking of working at a convenience or a grocery store such as, Rite Aid, Stop and Shop, CVS, and Walgreen. Also I'm still applying to different places so I was hoping anyone could give me advice on applying and WHERE to apply or if I have a good chance at any other places. Thanks.