First, is the radio a DSC radio? Does it have a Distress button covered by a small red plastic cover? If so, you can go into the menu system in the radio and pull out the MMSI number that is set in the radio (if the previous owner did that). Every make/model of radio would have a different menu system, so find the manual for yours and it would tell you how. Once an MMSI has been entered into the radio it is not recommended that you try setting a new one in, use the existing one and re-register it in your name. If the previous owner never entered an MMSI number, then you would apply for a new one and enter it in the radio. Remember that you must have an ROC(M) – Restricted Operator Certificate (Maritime) in order to use a VHF radio. Self study courses are available online through Canadian Power and Sail Squadrons.