Change BGM for Encounters

Question after Question :/ . I would like to know how to change the BGM for encounters (like a legendary encounter). Please don't chastise me for not going to the wiki, because I cannot access it.

1. open event page
2. right click >insert
3. on the first page of the "event commands" tab that opened, look at the right side, bottom section
4. choose the option "change battle BGM"; the 5th from the bottom

No offence, but this is pretty basic RMXP stuff.
It's 5th from the bottom of the first event options page.
'Change Battle BGM'