I will assume you can actually see and use the external drives/disk with your Mac file manager, in other words, that they are mounted properly, as that seems to be the case from what you wrote.
Adding drives can be done manually, as stated here:
An easier, but longer procedure, goes as this:
Go to the bottle manager, which "can be run by selecting Manage Bottles from the Configure menu" ( http://www.codeweavers.com/support/docs/crossover-mac/officesetup
). Go to the "control panel" and use winecfg ( http://www.codeweavers.com/support/docs/crossover-mac/controlpanel
In the "Wine Configuration", you'll see a "drives" tab. You can add a drive letter (like "D:" for instance), which you then associate with the path to your external drive, as an example "/media/ext_librairy" (without the quotes of course). Since I don't know the path to your drives (and I don't own a Mac), you'll have to figure that one out. The point is to end up having a drive listed in the windows which points to where your real external drive is mounted. Add as many drives as needed if you have more than one external drive. Mind you I could post a picture of WineCfg in action, but it would be in french...
The fact that your drives are NTFS isn't much of a concern, so long as your Mac is capable of reading/writing to the drives once mounted.
The procedure is pretty much the same as under Linux, so I wrote it down here. Which of course leads me to say that an actual support ticket might be more useful to you, as the Crossover staff is very helpful, and I'm sure they know more about macs than me. Besides, the fine print says "This is not a support forum. If you need product support use our Support Ticket System. "!😉