Pull the carpet back that covers the gearbox tunnel... there will be a rubber plug (about 2.5" across) on the lefthand (passenger side) almost to the top of the cover and about a foot back from the firewall. Remove that plug and you will find the dipstick.
What you have there is a cap about an inch+ across that simply lift out... may have to twist it a bit to loosen it up but it is just a friction fit (like a cork in a bottle). If I recall right the little dipstick just has one mark which is the correct level. Add (if needed) thru that same hole.
Pic now attached, note arrow pointing to hole