Why won't my still photos in Final Cut pro X apply to timeline

I am making a movie using some still photos in between my videos. When I try to drag the pictures I want to use in the timeline that is already in the final cut's photo browser, it has a circle with a dash through it and won't let me insert any photos.

HAS ANYONE HAD THIS PROBLEM I NEED HELP RIGHT AWAY????

I have looked online and on youtube videos to solve this problem I don't get what I could be doing wrong.