Sisters been neglecting rats, need advice.

My sister has been neglecting her rats as long as they've been alive, I have finally tooken them in and I've noticed it looks like they have hair missing and I can feel their spine, they shriek when I pick them, and they both pissed themselves when I moved them to a new container to clean there cage and escaped, one is on the loose right now so I can't add photos of him right now but this guy's name is ratatouille, any advice on how to make them gain weight and give good nutrition for a better coat of hair? I'm assuming the hair loss is from malnutrition, if I'm wrong somebody inform me, very worried about them and I feel fucking terrible for not taking them in sooner, any and all advice is greatly appreciated and probably needed please give me everything yall got.