Transmission

It's an automatic transmission. The first problem started out with the check engine light. I thin brought out my ECU scanner to detect the problem. It gave me a code that I was unfamiliar with but when I checked up on it it told me the problem lies with heavy shifting. Mainly shifting from 1st to 2nd then to drive. My question for you guys is what is the necessary steps that I need to do in order to take care of this problem without going to the dealership. Thank you for your time