Problems with addiding short images to video

While trying to get an added image exactly where I want it and how long I want it is very difficult. The controls of left and right arrow do not work to allow very small, incremental movements through the video channel in order to trim the added overlay images. Very frustrating. Also on adding titles, they sometimes do not change color backgrounds the way they are supposed to--cannot actually get the black color background and change it. Again, very frustrating.