The manuals are located at SME Server:Documentation.
The documentation section contains the manuals and is an extensive source of documentation. It is a must read for everyone who is willing to use SME Server. It may be large and overwhelming to you at first, but experience, over time, has proven that a lot of problems could have easily been solved or would not have existed if users would have read them. It is also worth to re-read the manual after working some time with SME Server as a lot of information that did not stick or did not seem interesting at first might very well be interesting once you gained experience with SME Server.