create drop down list in forms

Is there some easy clear instructions on how to create a drop down list in a form using a text document for the data to load

Instructions may be clear but easy may be doubtful. What is not easy is that your question is not really clear. Where is this form - Writer, Calc, Base? What is the data like & where in the text document? A sample of such may be of help. It would help here if you tagged the question with something other than "common’.

To back up what @Ratslinger wrote, see guidelines for asking.

I am not sure I can answer this as clearly as you might like, but the process is called Validity. You essentially create a "list of cells that contain the information you want the user to select from. You add Validity (and reference that “list of cells”) in the cell into which the user’s choices should be limited. Hopefully, this makes sense to you.