Barrie,
There are several possibilities.
What the makers intend is that you use a short length of threaded rod (2mm or an american size) You screw the rod into the inner snake and then screw a clevis (or ball connector) onto the exposed end of the rod - locking with a locknut if you feel like being very secure
Or you can use a pushrod connector - length of wire with a threaded end. Thread the end into the inner snake and either bend a z-bend in the wire to fit through the rudder arm or whatever, or pass the wire thru a screw-clamp connector.
Or.... Sorry, I don't know how familiar you are with connection fittings - there are several other possible solutions but I wouldn't like to try and teach you to suck eggs.
How long is your route to the rudder? These gadgets are famous for expanding and contracting more than the frame they are in. This won't worry a boat driver much (but it sure makes model flyers sweat), but please remember to support the "outer" at (at least) both ends and have as little inner sticking out as possible (to support the outer - glues don't like to stick to it - wrap with masking tape before gluing)
These are links to the sullivan site - the ones you have got are not Sullivan, but the instructions may help
http://www.sullivanproducts.com/S503Nyloncontrolset.pdfhttp://www.sullivanproducts.com/GoldnRodContent.htmLubricate with water or silicone lube, or one of the oils for model racing cars made for plastics
Give it a whirl and keep asking!
andrew