Hola Jamie,

I understand it is a bit confusing to see that statement in the lesson; we need to re-word it so it is clear. What we meant by only using ningún/ninguna at the beginning of the sentence is that if you don't start the sentence with "no", then you need to place ningún/ninguna in the beginning. For example, you could say either:

1. No ha venido ningún invitado. (No guest has come.)

2. Ningún invitado ha venido. (No guest has come.)

Both are saying the same, but 1 is using the double negative "No....ningún/ninguna" in which case "No" goes at the beginning, and 2 is using only "ningún", in which case it goes at the beginning. When only using ningún or ninguna, then it needs to go at the front.

This would be incorrect:

"Ha venido ningún invitado."

I hope this clarified it.

Saludos

Inma