I am new to property taxes in Ontario.in the property tax section there is a block written"home energy cost"how does it work?do I add up all my hydroone & uniongaz bills?

Yes. If you lived on a reserve in Ontario, you should enter the total of the amounts you paid for 2017 for your energy costs (for example, electricity, heat) for your principal residence on the reserve.

https://www.canada.ca/en/revenue-agency/services/child-family-benefits/provincial-territorial-progra...