if you post the make (and model if possible) of the lathe you may get some help with this. every maker has their own scheme of controls.
In the meantime, flip your cutter upside-down and get to work!
**EDIT**
oops, sorry, just realized the make and model were in the title. Don't see much about them on the web aside from a flashy catalog. You could try calling Trens' tech support and see if they will help you. Often they have operation manuals available online for download.
good luck!
Will-