Graphics

Hi All, I'm hoping to get some help with a basic Dashboard question.  If there is a better forum for this, please let me know.

I am looking for a step-by-step guide for dummies to help me create an editable DashBoard  list, and have that list populate a dropdown.  I have managed to do this a couple of times by sort of copying an example that I have, but it is unclear to me exactly what I am doing.  I end up just copying some of the parts of the example that I have, modifying them, tinkering with them, and eventually I can usually get it to work.  The issue is, I think my example has way more elements than are necessary, and I'm not sure what elements are truly necessary and what elements are not.

This is something that I will likely need to create a lot in the future, and at this point it usually takes me 30-60 minutes of trial and error to make it work.  If anyone can provide step-by-step instructions of exactly what is necessary to accomplish this, and maybe and explanation of what exactly is going on, it would be super appreciated!

For bonus points:  Is there a way to have my list populated from a spreadsheet, instead of filling it in by hand?