Tough job to screw up!
I used a "pre-mix" by Peak, I think, maybe Prestone, safe for aluminum engines.
You will have to remove the tupperware on the right to get at the filler cap.
Service manual suggests filling very slowly to avoid trapping air.
I did exactly that then let her run 'til the fans kicked on while monitoring the level in the radiator.
Once cool enough to get near it, I filled the overflow to the full mark and put her back together.
Make sure all your hose clamps are tight while you've got access to them!
Come to think of it, it's been 2 years so I'm due.