If social workers are not involved with the family, then you and the parents can agree that the child will come and live with you, so you should speak to the parents directly.
You will need to explain to them why you think this will be best for their child. For example, you will need to explain how you can meet the child’s needs in terms of day to day care, education, keeping in touch with family and friends etc and what support you will have to ensure they get the best possible care in your home. It is a good idea to explain this in a letter and keep a copy for yourself.
If social workers are involved and the child has a child protection plan, you should talk to the social worker about the child moving to you. The social worker’s job is to try and make sure that the child does not come to any harm. The social worker might want to make some checks on you before the child moves. This would be so that the social worker could feel sure that it would be safe for the child to live with you.
If the child is likely to live away from their parents, there might be a Family Group Conference. This is a special sort of family meeting, where everybody gets together and decides what they will do, as a family, for the child. The social worker might decide to call a Family Group Conference, but you could ask for one to be held.