Since Google Classroom is a competitor to Canvas, it doesn't really make sense to try to use them together. You can provide a link to your Google Classroom from your Home Page in Canvas or as an item in a Module, but there isn't much reason to do so.
Canvas can and does work with Google Drive, which exists independently from Google Classroom. Are you working as part of an institution, or do you have your own Canvas account?
The Google Assignments LTI is a useful tool for those who are used to Google Classroom and are looking for similar behavior in Canvas. But I highly recommend that you choose one or the other and then use it to its best functionality without trying to make one behave like the other.