Approach a recognized / licensed adoption agency in your area. Meet an experienced social worker at the agency who will be able to explain to you the legalities and procedure in detail.
Do not make the mistake of going to people who promise a quick, hassle-free procedure in exchange for large sums of money or unlicensed organisations that claim to be adoption agencies. Similarly, avoid the temptation of going to a nursing home or hospital where they may be doctors who hand over new-born babies to people looking to adopt (either from the goodness of their heart or as a baby-selling business). Such forms of child adoption could lead to serious legal issues at a later stage as they could be forms of child trafficking.