Ronfold - I use a program called Gimp, its like Photoshop but free.
Open your picture in it then choose Image->Scale image, and shoot for around 150 x 150. I tried the max 240 x 240 and it looked way out of place on the forum.
After you scale save it, choose File->Save As. At the bottom of the Save Image window you’ll see a drop-down that says “All Images”. Change that to say JPEG image, then hit Save. A window will open asking you to choose the Quality, the default 85 should be just fine. If you keep it under 240x240 and save as jpeg it should come out under the max size of 14KB.
Let me know if you need more help.