CtB maps are generated directly from the osu map, yeah.
There is a few guides out there about creating beatmaps and using the editor. It will take a bit of getting used to, but once you get the hang of it it will be second nature. The hardest part for most newcomers about beatmapping is getting the timing right. I'd recommend uploading your map to the beatmap help forum, and I'd be glad to help you out with the BPM. It's best to make sure you have the BPM spot on before you start the actual mapping.
There is actually a beatmap creation entry in the FAQ, which should answer mosts of your questions:
http://osu.ppy.sh/?p=faq&n=5Good luck, don't be afraid to ask for some help on IRC.