If you're worried because your image size seems to be too large, don't worry, once you submitt the post it converts to standard size.
If your image is small it will keep being small after posting unless you change its size in "Paint" program, for example, before adding it to Steemit, of course.
Side by side depends of the images sizes, but it the size allow it, just post image>keyboard bar>post image. They will appear sde by side.
Above the other, post image>keyboard intro>post image.
There are HTML commands for that, but knowing that is enough atm for a proper result.