The steps to become an MOU signatory are very straight-forward and less formal than for the Convention itself or an Agreement: 

Decide to become signatory after reviewing the MoU. The governmental institution that would be responsible for the conservation of the species, and therefore for the implementation of the MOU, first needs to decide to become a signatory. This would usually be for example either the Ministry of Environment, the Ministry of Agriculture or of Fisheries depending on the species concerned. National procedural rules may require consultation of other governmental authorities or even an authorisation of the respective Minister. 

Sign the MOU. The competent official of the responsible governmental institution signs the MOU in the presence of a CMS official at a mutually agreed time and place. Most often the responsible official is the Minister of the respective ministry comptetent for the species. In case the Minister is not able to sign in person, his or her designee may sign on their behalf. But unless this person is the deputy Minister, they would need a written authorization (an instrument of full powers) from the competent Minister to sign the MOU in his or her place. In addition, according to the Vienna Convention on the Law of the Treaties, the Ambassador of a country has the power to sign MOUs. 

The original version of the MOU is signed and kept by the CMS Secretariat, which acts as the MOU Depositary.