I don't know if you've had to adjust post-processors before but it can be a bit tricky. I've not ever worked with lathe posts, just milling, but perhaps the process is the same.
The post-processor stuff you can change in Creo ("Options File?") will let you adjust certain aspects of the output. Sometimes that's all you need to do - go in there, turn on/off options, and it works out okay.
If the settings in Creo are not providing you with the correct final output, you might have to go to the next step of complexity: editing the FIL code associated with your specific post. This is more difficult, because it's actually programming the post to handle specific cycles it's seeing.
The last thing I could suggest is looking for other post processors, if you can't find one specific to your machine. Look at the lathe itself or the manuals for it to find out what it's using for it's controller, i.e. Fanuc 35i or whatever, and maybe there's an existing post that handles code for that controller that will work for you or is easy to adjust to get the desired results.
