First question - What kind of water heater do you have?
This link was just the first one I found, but I don't know if it's the brand of water heater that you have. If it's not, search for a DIY video for your brand.
https://www.youtube.com/watch?v=xu9EqCPmLOkThe electric water heater element will be on a breaker, not a fuse.
As mentioned already, if you are not comfortable working with 110V power, then you need to find someone that does know how to work on live voltages.
And last, never turn the 110V water heater switch to the on position if you do not have water in the heater.
