looked up the mower model and got the engine info. heres a diagram of the carb.
http://www.searspartsdirect.com/partsdirect/
showSubComp.pd?imageUrl=http%3a%2f%
2fc.searspartsdirect.com%2flis_png%2fPLDM%2fP0204119-
00001.png
the red nozzle goes inside the carb in one of the side holes but its hard to tell without seeing the carb. all i can say is try the different spots it will fit unless the nozzle broke off in which case you will need to remove the old piece and get a new nozzle.
FYI your engine model is 143.046702