how does confederation provided Quebec and Ontario with sovereignty?

This is actually a pretty detailed question for this short-answer space. Québec’s entry into Confederation is deeply tied to that of Ontario's. Together, the two were united into the Province of Canada in 1840, in response to the rebellions in Lower and Upper Canada, and the Durham Report of 1839. Check this our:

https://www.thecanadianencyclopedia.ca/en/article/quebec-and-confederation