How and what do I need to get custody of my younger siblings

While I am a licensed attorney in the State of Arkansas and not New Mexico, I will tell you that you would have 2 options in Arkansas. The first would be to file a "FINS" (Family in Need of Services) petition with juvenile court to try to have the children removed from their parents' custody until such time as their circumstances change and they are in a better place to provide for the health, welfare and safety of their children. The second option would be to file a petition seeking guardianship of your minor siblings. As their guardian, you stand in the shoes of their parents and can make decisions for them. In Arkansas, you have to prove that both parents are "unfit" to get a guardianship, if either parent is going to contest it. I recommend talking to an attorney in the community where the children reside to discuss if either of these options are available to you.