HOW TO USE A THESAURUS
A thesaurus is a book that lists words or phrases that mean the same thing or almost the same thing–a book of synonyms. Some thesauruses list words in alphabetical order, just like a dictionary; however, many don't. They have an index at the front, with instructions of how to use the index to find the word you want. Read the instructions.
A thesaurus can introduce you to new words, or it can suggest words that you already know. For example, you might find skinny, svelte, thin, emaciated, and skeletal as synonyms of slender, yet each synonym leaves a different impression: skinny usually means too thin and weak, svelte means fit and thin, emaciated and skeletal are thin to the point of sickness or death, and thin means little or no fat. Only thin and svelte provide approximately the same tone and meaning as slender. So the thesaurus may introduce you to many new words, but you ought to use the dictionary and/or other resources to understand the synonyms it exposes you to.
Simply searching for the new word on the internet may sometimes give you a clue as to how a word is used. One good web site for finding a word used in context is www.Bartleby.com. You can search for a word and find how other authors have used it.
In any case, look through a thesaurus and you'll find many riches to help you express yourself!