Added brief statement about YubiKey Prompting

content/accounts/setting_up_and_using_duo.md

@@ -156,6 +156,9 @@ entered manually to complete the login.
 {{< figure src="/images/5832710.jpg" height="200" caption="Photo credit: Yubico" >}}
 
 YubiKeys are USB hardware tokens that generate passcodes when pressed.
+With HCC clusters, there is no prompt to press on the YubiKey. When the DUO prompt
+appears in the terminal, press the YubiKey and it will output a string to the terminal
+to authenticate you.
 They appear as a USB keyboard to the computer they are connected to, and
 so require no driver software with almost all modern operating systems.
 YubiKeys are available from the Husker Tech store at UNL. Users may also purchase them directly from