I put them on my RV6 same as Rosie did....matter of fact he may have given me the idea way back when. I'm REALLY glad I had them.
Just get an 'assortment' of springs from your local hardware...I like the ones with the big 'J' hook open end. You can even cut and rebend the 'J' to get the proper length. One end goes over the gusset on the pedal for the cable bolt and the other end hooks to a 3/32 hole you drill in the firewall angle stiffener directly forward of the rudder pedal gusset. The 'closed' end springs are 'ok' but are a little more difficult to work with. It's that simple...no pics required.
I used springs on both sides of my RV6....the px seat right pedal and the pilot seat left pedal.
You can experiment with the spring tension to get the 'feel' you want. Once flying....I ADDED a smaller diameter spring INSIDE of the spring on the right side. This put a little more 'tension' on the right rudder to keep the ball smack dab in the middle...no trim tab on my bird.
As Rosie mentioned.....the springs keep your rudder from flapping and banging all over the place when the wind is blowing on the ramp as well. They also keep the cables taught at all times....no saggie cables hang out on the flight line either.
As far as I'm concerned.....don't leave home without 'em

!!