actually I found out that I don't need checkboxes. For my purpose, the "select menus" field was actually far better suited. How these types of fields are used is explained in Jaxel's tutorial on the embedding of images, see here:
This video is expansion of the previous tutorial (http://8wr.io/threads/video-tutorial-advanced-scripting-and-coding.2/). As such, I will only be listed the new code added in this video. Page HTML: Page CSS: .countries { position: absolute; top: 10px; } .countries.c1 { left: 10px; }...
8wr.io
There you will find all informations needed to ientegrate select menus and also images.