Cash Quantity for Stock Orders

Why can I not see $ amount on order entry like this:

https://www.interactivebrokers.com/en/index.php?f=1656&nhf=T#cash-quantity

 

Since this is just a feature, you’d have to enable and configure it.

 

Where can I enable it? I've been looking and looking...

 

I believe that after selecting the quantity you get 2 options at the submit button: either to submit directly, or to see the margin impact. That will pop up another window which shows the total value involved, the estimated commission and the impact on account margin.