To split the event, place your curser on the frame where you want to split it and press “S”. Then to create a transition grab the right event and drag it over the left event. An “X” will appear in the overlapped area. This is a dissolve. If you want to replace it with some other transition go to your transitions box and drag another transition to the “X”. The transition will change. The length of the transition will be controlled by how much overlap you create. You might want to make sure that “ripple edit” is turned off until you learn how to use it – if you don’t know already.