Okay, so I can't go step by step with you guys since this is a very individual process. Building Characters depends on your writing style but there are a few things to keep in mind when building a character.

1.) Make them interesting: For the most part, characters are gonna be the center of your story. So if you don't have interesting characters driving the story forward your story will fall flat. A good way to do this is to give them conflicting personality traits. For instance craving acceptance but building a wall believing it will never truly happen. Or loving women but being terrible at wooing them

Example: Richelle Wolfenstein: Richelle is a character I made with quite conflicting personality. She wants to be accepted but she believes that no one ever will so she builds a shield around herself built of sass and sarcasm. However, when she finds someone who accepts her she is hesitant to accept them because she doesn't believe they truly accept her.

2.) Make a character ark: Okay this is pretty basic. But many professional writers forget this step and it really bogs down the work. Or they have the same lesson over and over. For instance, Fluttershy learning to stand up for herself. She learns it again and again.

Example: Richelle Grayson: In my book "Life and Legacy of Richelle Grayson" she starts out with an ark teaching her to be wary of the world and not just trust the first person to tell you what you want to hear. But then she has to have another ark where she learns that not everyone is like that and she just needs to know who to trust instead of trusting no one.(Not there yet but we will get there) 

Those are the two basic rules of character building. I'm sure you'll find many others with other advice but those two details should be enough to get at least a character built and then you have to incorporate them into your story which is a different chapter.