I think it tells ya in this thread, which I always recommend to new folks. READ THIS FIRST If the instructions are not there it's pretty easy. When you are in the editor where you type words, look down and see a paper clip Drag files here to attach, or chose files.
Pictures stored on your device can be added there. Just be sure to resize them by double clicking on the picture after its been placed into the post, a pop up box will appear. I use 500 for the width and tab over for the height which will take care of itself. You can edit the post for 30 min and do the same by douple clicking the picture.