In the basement you should have a waste stack serving 1st floor fixtures and a vent stack venting the basement fixtures- that is a common vent- it serves 2 or more fixtures.
Tie into the common vent or make one if you don't have any plumbing there yet.
Do not vent into a waste stack- vent stacks only
Where I get confused is that I know you can wet vent fixtures that are on the same floor but lets say I added a shower in the basement wouldn't I have to extend the vent pipe up and over the first floor fixtures and tie into the stack to avoid the wet venting?
If the fixtures are stacked then revent. Or separate if its not practical. You are asking a question that has no definite answer.
I read the article on circuit vents but am still confused. What exactly is that? Does that mean the drains for the fixtures run horizontally and eventually drain into the vertical main waste stack? And a separate vent stack is used for these fixtures?