For the coaches file, you would use X's editor to import the file at the start of your franchise. For the draft picks, do the same but after the season.
As for ratings, there is no formula. I use a combination of my own personal knowledge, their scout.com stats, and YouTube to come to a conclusion. I won't be doing a 15 unless someone wants to lend a hand. It's a lot of work doing a class by yourself.