IF you know how long the event is you can put the cursor in between the 2 clips then go under insert-Time and then enter the length of the clip. If you don't know how long it is look in the manual under Ripple Editing, that will teach you everything you need to know.
Basically just park the cursor where you want the new image go go, turn on ripple, (CTRL+L) and drag the new image/file to the timeline. Everything will shift downstream for the length of the new event/file. By downstream, I mean everything will shift to the left, making room for the new file.