Hey Cat333,
I was curious about this a few weeks ago, too. So, I managed to get two different templates to lock an episode.
The first one is:
label dontread
NARRATOR
This chapter is not ready yet.
goto dontread
The second one is:
label name_input
input What’s The Password?|What’s The Password|Done(PASSWORD)
if (PASSWORD is “mypassword”) {
NARRATOR
Access granted.
goto start_story
} else {
NARRATOR
This story is currently unavailable.
goto name_input
}
label start_story
I prefer the first one, because it’s easier. 
Love A-W