I didn't send you a screenshot -- I sent you two.
The first screenshot (how to configure your currently-connected ereader) shows you how to find the second screenshot (configuring your ereader to accept specific formats and which ones take priority).
It does assume your ereader is plugged in and recognized by calibre -- because if calibre doesn't see your ereader, how can you send either AZW3 or MOBI to it?