adding picture in between two pictures...

ok i know this might be the easiest thing in the world but i just cant seem to figure it out, o have vegas pro 8 and i am making a montage for my church, well each class has a title and a class photo. i put those in the first day and now have all the picture dont and go back to start placing them in between each of the class photos and titles only to find out that vegas just places the picture under the next file. is there any way to make vegas place the new file "inbetween" two files already on the timeline so it just slides the rest of the files down, instead of just overlapping files? thank you very much