How to Use Canonical Tag?

Question

I’ve tried help on the net, but I can’t figure out how to resolve this issue.

For example: if you have the url - https://www.seusite.com/ and google assign as canonical https://seusite.com , which url to add the tag in https://www.seusite.com/index.html?

https://seusite.com/index.html” /> ?