Quite a few manuals are available for LabWindows/CVI. They all install with the software, but you can also find them online by doing a search for "CVI manual" on www.ni.com. The main manuals are the User Manual and Programmers Reference Manual.
Also, for a more tutorial approach to CVI, consider the CVI course. The course is available in instructor led (both at NI headquarters and onsite), as well as self-paced. To order the courses, goto www.ni.com >> Products and Services >> Services and Training >> Training.
Regards,
Greg Caesar