Itd help a little if you could tell us what you find confusing the admin guide is pretty linear and covers setting up subscribers, templates, classes of service and discusses preparing users for use of the system etc
the 4.0(4) version can be found here:
http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_administration_guide_book09186a0080228436.html
Theres also a maintenance guide that talks about ongoing care and feeding of your Unity system which would be a good thing to review if this is your first exposure to Unity:
http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_maintenance_guide_book09186a0080228417.html
If theres something more specific youre not sure about or theres something in particular in one of the guides you dont understand, let us know and well try and help.