Write your college essay. Transition words are common in everyday speech and it's likely that you will naturally include them in your rough draft. However, learning how and when to use them is best attempted in the revision state of your essay.
Proofread your rough draft and mark the locations of where your ideas begin and end. Sometimes an idea can span several sentences and sometimes a single sentence can have multiple ideas. Identifying where in your writing your thoughts shift is paramount and may take some time getting used to. If you struggle with this step, you may want to research and learn how to organize your writing.
Identify the relationship between one thought to the next and find an appropriate word or phrase to transition. For example, if two thoughts are they related to each other, you will want a word that establishes that identity. For example, the transitional word "additionally" signals several things to the reader; it queues the conclusion of the preceding thought, indicates the beginning of a new thought and establishes that the two thoughts will be concurrent. Please note, there are transition words that can indicate the extension, addition, contrast and emphasis, to name only a few.
Revise your revisions. Good communication requires fluid movement from idea to idea. Reread your edits and make sure they flow naturally. Odds are that if it sounds awkward, you may have incorrectly identified where an idea ends or begins. Remember, your composition professor may have dictated to you that transition words are necessary for good writing, but there is a difference between using transition words and arbitrary inserting them into a college essay.