The video I linked above shows the basics. A detailed map would be a great help for you. It sounds like you did use Google Maps for Venice Italy, so you probably know how to click on the satellite view and zoom in. That gives a better idea of the area.
As you consider places to stay, you could Google them to find out where they are and get walking directions from the closest vaporetto stop. You can also use Google Maps to get walking directions to places that don't involve a vaporetto, although just following your nose may be more fun.
Note that those beautiful curved bridges actually have steps. They're usually shallow, i.e. wide tread and short rise, so rolling any kind of bag over them isn't too much of an issue -- unless you have big and heavy luggage.
As a solo traveler, I travel light with a 2-wheeled roller bag that weighs 20 pounds maximum fully packed. I was 71 years old the last time I was in Venice and I did just fine. If you follow the frequent guidance to pack light, it will help with your whole trip to Italy using public transportation (especially trains), not just the Venice part.