I'm on quest making a game book. Pretty new to the whole thing, but I'm having some trouble. So lets say I have "passage 1" and "passage 2". I'd like to display a message in passage one, but only once the player has already viewed passage 2. So after they view passage 2, the text in passage one will now display indefenitly.

Probably a simple solution, I just can't find it. Also I'm editing online.

Assuming you're in Gamebook mode (with pages), rather than Text Adventure mode (with rooms).
Make "passage 2" type 'Script + Text. Add a script to set a flag to ON. Call it something like 'HasSeenPassage2'. When the player visits "passage 2", the script fires and now the game knows that the player has been to "passage 2".

In "passage 1", use {once:Your Text Here} to display text only the first time "passage 1" is seen. Use {notfirst:Your Text Here} to display text only after the first visit. And use {if HasSeenPassage2:Your Text Here} to display text for after the player has seen "passage 2".