I put guided it around the down tub to join the rest of the cables as they come out of the shock mount. Added a stick on mount half way around the left hand side of the down tube to hold it off the frame as it wrapped around. I used zip ties to make all 3 cables (4 when I had a reverb) come around the right of the head tube as a bundle.
Or go 1x 10/11 and do away with the mech 😀 which is what I have now.
Edit: did you mean as it goes around the BB shell, if which case yes there should be a plastic guide that plugs into a hole in the BB shell. It one of those nasty exposed cable types ones that should have died last century.