As you have already been informed, there is a dictionary and half of it is actually a description of the grammar. As such it is an essential tool for helping to learn Klingon, no matter where or how you are learning it.
When the dictionary was written it was sort of written as a joke. The linguist writing it (Dr. Marc Okrand – a friendly, intelligent, and funny guy if you ever get the chance to meet him) took the language seriously (mostly), but assumed that no one would actually go so far as to learn this language that he created, so did not always take the instructional role of the book so seriously. Unfortunately, this means that it is not always so good at actually teaching you how to speak the language. All the information is there, but it takes some effort and dedication to use it to learn to speak the language. There are other tools out there. The best may be the Learn Klingon Online course, right here on the KLI webpages. But you will still probably need The Klingon Dictionary as an additional reference to look up the details of something you don’t understand or need to refresh your memory of.