My childs mother is currently homeless and I have all of her children. They will be finishing the school year with me? How can I take custody?

My daughters mother was recently kicked out of her current living arrangtement. She has no home and has withdrawn all of her children from school. The 3 children are currently staying with me and finishing out hteir school year around where I live. THeir mother has a history of cutting herself and an attempted suicide within the last year. Only 1 of the children is biologically mine but I take all 3 children when I get my daughter for visitation. Their mother does work and is looking for a place to live but the children will still be finishing school here. She currently lives approximately 2 hours away from me. She refuses to move closer to me and I just want my daughter to be close to me so I was hoping because of the circumstances I could take custody of my daughter?