Today I'm going to give you a huge tip on how to get through agents and editors slush piles. This is a pet peeve of most in the industry as it is a sign of lazy writing.
One of the biggest pitfalls of writing, and one of the top 10 reasons I reject a manuscript, is telling instead of showing. Telling is passive writing. Or to put it another way; it is the telling of something that has already happened and is in the past. Not to be confused with past tense, that's entirely different. Past tense, present tense, those are styles you choose to write in (I'm actually a huge fan of past tense. I prefer it). Telling is more akin to information dump where you go into backstory of some kind or another that the character is recalling (not to be confused with a flashback. That doesn't mean you can do it as a flashback and get away with it with me. I dislike flashbacks immensely).
Showing is active writing of something that is currently happening. There is a time and a place to tell instead of show, but it needs to be done sparingly and appropriately. In the beginning of your novel is not the place to do it. A good rule of thumb is to do your best to not tell, info dump, or give back story for at least the first ten pages.
Until the reader cares about your characters and is vested in them you don't want to go into backstory. Your first chapter needs to hook the reader, entice and interest them with questions and mystery. Only then will they keep reading and tolerate things like backstory. When you do add it in later remember not to do an information dump where you just 'tell' the reader the backstory. Try to 'show' it and work it in naturally where it fits with things that prompt it.