I haven't used the Dashboard, but I'd guess that others get images from it by the "Print Screen" button, pasting it into a program then cropping the image, saving it and uploading.
The cropping can be done in Paint or Photoshop, any graphical program anyway.
Well actually the program itself has a feature for that . No need for paint of photoshop, just click the 'Export Image' option under the Export menu. The blue transparant overlay is the area that will get saved, it automatically overlays the part you're (most likely) interested in ie. When looking at the profile page of a race it will overlay the profile, when looking at results from a race it will overlay exactly the table with results and nothing else, in fact, if you are just interested in the top 5, select the first five rows of the table, hit 'export image' and you'll see it automatically overlays ONLY the first five rows If you want another part the overlay can be positioned and resized with the mouse and/or arrow keys.
After that, when you see the blue overlay either, double click it with the mouse, hit enter or do a Ctrl-C. The first two options save the image to the images folder which you can acces by selecting 'Image folder' option under the export menu and the ctr-c option will only copy it to the clipboard for when you wanna do some editting on it in photoshop or sth. When the image is saved it will automatically get a informative unique filename (for ex. AmsteGoldRace-Profile.Png).
In any case, have a look at the manual, i think there is a whole chapter dedicated to the image export thingie
