Something like a paramender would ideally sit between the tripod head and the camera, and should be firmly fixed to the base of the camera. The point of it is to move the camera up its vertical axis the exact distance of the lens separation, so putting it on the tripod with the tripod head on top of it would kind of defeat the purpose.
However it means it doesn't matter which way the camera is pointing or even if your tripod is remotely level, as the only purpose is to shift the camera along a set axis such that the lower lens moves to the same spot the upper lens had just been in. But the camera itself by no means has to be vertical and level. If you hold it completely upside down then the camera's vertical axis is now pointing into the ground.
Aren't relative frames of reference fun?
If you are handholding a Mamiya TLR with parallax indicator that is set to the correct lens adjustment, then you can carefully move the camera along an imaginary line running from the tripod socket up through the middle of the ground glass until the indicator line in the viewfinder is level with the top of where you want your frame. Easiest done when the camera it perfectly vertical, but can be done while it is tilted in any direction if you're careful.
Tilting slightly can work, but do keep in mind the slight shifts that can make in everything, which may or may not be important to your photo.
As for the red indicator: I've seen a number of other posts suggest that the parallax indicator IS the red one. As far as I can tell this is wrong and none of the models had a red indicator for parallax. Which is kind of sad because I actually find it brighter and easier to see in a lot of conditions I've tested my C330f in, but I will admit that I was initially confused when I first got my hands on mine. I may open mine up and see if I can't swap them, which may someday really mess with someone.