en.wikipedia.org
Basically, DSC is a button you push in case of emergency. It will send a distress signal to a monitored channel by the coast guard with your gps location. The MMSI is a number issued to you upon request that is unique to your boat. When you apply you will include details about the boat size, colour etc.
This document replaces Issue 6 of the Client Procedures Circular CPC-2-3-07, Maritime Mobile Service Identities (MMSIs).
www.ic.gc.ca
Your local Power Squadron does VHF training.
https://www.cps-ecp.ca/
Legally, you are meant to get a license and you can be fined for operating a VHF without one - although it would appear from the chatter on the radio that many acquired their license by watching the 1970's movie "Convoy!"
Be sure to do a radio check every day. Its the only way you can know you are effectively transmitting. I had to replace the diaphragm in my mike after about 5, 6 years.