Shirk & Kdeselms have it right.
To try and recover a lipo that has been discharge too low safty comes first. Try a lipo sack, ceramic jar or do it out side a safe distace from anything flamable.
Next start out at a low amp charge, about .5 amp untill the cells get back to a safe voltage then you can come back up to the std 4.8 amp charge.
If the pack is not damaged too much it will come back, even if it does seam alright watch it closely for the next couple of charges.