[stunsworth]

Anthony, ignore the dpi, ignore the size in inches, the only important thing is the number of pixels in each dimension and those are within the required maximum.

So, to make sure the file is small enough you need to save it as a Jpeg. This should allow you to specify the Jpeg quality. The lower the quality, the smaller the Jpeg. How you actually get to this stage will depend on the editing software that you are using. Lower the quality until the size is under the maximum allowed in the forum. Save the file and you should be ok to upload it.