My Rheem power vent 2 is two years old. I live in Scarborough and we are seniors and not too technical.
My hot water heater tries to come on. It gives a few clicks, starts up, then shuts down after a few seconds. I checked the electric point it is plugged into, but that is fine. How Can I fix this?

You will need to use a meter to find out what safety is not closing. You cannot guess at these things unless you want to risk dying from carbon monoxide or a fire. A safety is opening to keep it from doing something dangerous. Find out which one by testing them with a multimeter. Here is a manual: https://dl.dropboxusercontent.com/u/8010163/How%20to%20use%20Test%20Equipment%20Service%20Manu al.pdf
There should be a wiring diagram on the heater, or you can get one from the dealer. It will clearly show the test points.