What can help with dry,frizzy,slow growing hair?

I am 14 and I have a mix of 3B and 3A hair. My hair at the top of my head it's more 3A. It is the most frizzy and dry part of my hair. My there is also layered at the top could that be why it's frizzy and dry?I'm also trying to grow my hair. My hair broke off from heat tools and relaxers. 5 years ago I had it relaxed but kept using heat tools. I stop using heat tools 1 year ago. I would like to use Shea moisture or any thing that would grow out my hair. what should I do?