The map file came from Ontario Trails as an .img file. Once I created the "Garmin" folder on the SD card and moved the file to that folder I was able to enable it from the Map Setup on the GPS.
I also downloaded the Base Camp software from Garmin onto my computer and I was also able to download the update file for MapSource but I could not see the Ontario Trails .img file from within MapSource, but I could see it in Base Camp. Don't know how much I'll use the software on the computer but I'll see as we go.
Have not purchased any other maps as yet, don't really know what may be needed.
Thanks for the info