Hi @PhillipLuck ...
The "Sections" tab you are looking for would have had to have been manually created by you or another instructor enrolled in the same course. It's not an "out of the box" tab that Canvas provides. The only tab that shows by default on the "People" page is "Everyone". When you add tabs to the "People" page, those are Group Sets. So, for example, you might have a group set with the same name as an assignment name in your course...such as "Written Paper". Then, within that Group Set, you would create groups in the group set. For example, you might have "Green Team", "Blue Team", "Red Team", and "Yellow Team". Then, you assign the people to each of those groups. You could then have a totally different Group Set for a different assignment, create group teams in that Group Set, and assign students to those groups in a completely different way than you did with the first Group Set. The Group Set name and the group names within those Group Sets are totally up to you.
@stimme is correct that "Sections" are found within the course "Settings" page, but if you are looking to set up groups like I've described above, then you'd want to use that instead.
As for rubrics, there should be a "Rubrics" course navigation button on the left-hand side of your course where all your rubrics are located. You can add any rubric from that page to a graded assignment, graded discussion, or a graded quiz.
Does this help at all? Keep us posted...thanks!