Hooo... that's a heafty question. Can I ask how long you've been playing guitar? It is good that you want to train your ears as that's, in my opinion, the truest way to compose. But the catch is there is no way to get fast results from training your ear. It takes a lot of time and a lot of dedication. If you start to slack up your progress will quite literally back track. Most, if not all, people will charge you for their services too, some are good on price, others are incredibly expensive. Other than that, if you're willing to shell out a few bucks and a lot of time, you will happily understand music on a higher level. That being said you can probably find something through google if you search for ear training there. That being said, good luck to ya.