A government needs to ratify or accede to the treaty in order to become formally bound by its provisions.
Accede
Accession is the procedure open to governments that did not sign the treaty when it was open to signature (between December 1997 and March 1999).
Firstly a government needs to follow its own stipulated procedure for joining an international treaty e.g. submitting it for the approval of the national parliament or assembly; and secondly, the government should deposit an instrument of accession at the office of the United Nations Secretary-General in New York.
An instrument of accession is a document in which a government declares its acceptance of the treaty and commitment to its implementation.
Ratify
Ratification is open to signatory countries who signed before March 1999. The process is similar to that of accession: first take the required steps at a national level for joining an international treaty and second submit a document to the UN.