Tamiya mechanical legs - using with radio

[mikesinden]

Hi, please help, I'm not an idiot ( well maybe ) I've just brought a knight hauler and flat bed, I'm a complete newbie to trucks, but not R/C.
Reading through the legs instructions it claims, to dismount right stick down to lower legs, I understand this, that's the easy bit, but it then says left stick forward to disconnect 5th wheel........... How ?
I thought I'd be setting left stick for gear change and motion, if I do as it claims, pushing left stick forward will simple drive the truck, where, how, does the disconnect come into it ? Should I be setting my 5th wheel servo to another channel to disengage, do I us a 'Y' joint to join both servos or is it simple MAGIC with the 1/14 fairies doing the work.
Please help.
Mammy thanks in advance.
Oh, incidentally, I do have the option of two radios, both futaba, one 4 ch one 6 ch.
mike