Hi
Not a dumb question. (Might be a dumb answer though.🙂!)
OK I assume you are creating all these images to use in a Stop/Motion scenario and you want them to be played back at 15fps. The first thing to do then is to set your still image duration to 15 fps or 1/15 seconds = 0.066 seconds
This is done in Options/Media/Default still image duration
Load all your images to the image bin and use use Ctrl A to to place them onto the timeline. For a start you may not see Images on the timeline, only a series of very close vertical line but by zooming in they will become visible. It may take a little while to cache/render all the thumbnails. It depends on how many images you have and their resolution.
Assuming they have been added in order the time line will play back at 15 fps.
At export set the fps as Custom 15fps and tick Constant frame rate.
This should give you something near to what I think you want.
Nat