Hey dear, you actually put it only at the end. When you put it at the front, then it goes separated from the word. I don't know what is the rule for that, but it has to do with different tenses, for instance in the imperative it goes at the end, while in present or past it goes at the front. I suggest you make a specific question about a case in which you have to say it, so I can tell you which one and why.
