When using the calculator widget

How to I make the answer look like a dollar amount after all the fields are totaled, ex: $150

You need to add the dollar sign manually in the Form Calculation widget. Here's a screenshot: 

Here's the result:

How do you put the "$" into the widget box area?  It won't let me click in the front of the box to insert the "$".

I just hover the mouse at the window box area. Try at the very corner of the box or hover your mouse at the middle of the added field (blue highlighted text). Here's a screencast that you can check:

Please try it and let us know if you need further assistance. Thank you.