If you downloaded it from the link I provided above, then, according to the readme file, you should be able to simply double-click the scripts package (most Adium extras install this way) and it should install for you.
Then, when formatting your message you can use the following commands (this is in another readme file that is buried within the scripts package...right-click>show package contents>Contents and there they are):
"Now Playing
Now Playing checks the currently playing track in iTunes and returns it to Adium depending on the displayFormat string.
/nowplay{displayFormat}
displayFormat - The string that defines how the current track is displayed.
If iTunes is closed or stopped the script will return "silence...". Otherwise, the script returns the current track based on the string displayFormat and the wildcards within it.
%% - Displays a percent sign (%)
%< - Displays a comma (,)
%o - Displays the playlist order number
%a - Displays the artist of the song
%n - Displays the name of the song
%l - Displays the album of the song
%g - Displays the genre of the song
%t - Displays the total time of the song
%c - Displays the play count of the song
%b - Displays the beats per minute (BPM) of the song
%d - Displays the last play date of the song
%e - Displays the short format of the last play date of the song
%m - Displays the last play time of the song
%r - Displays the "out of 5" rating of the song
%p - Displays the percentage rating of the song
%s - Displays the star rating of the song
For example if displayFormat equals "%n by %a - %s", the script may return "Another First Kiss by They Might Be Giants - ?????". Any other percent sign-character combination will be filtered out without replacement."
As for typing "/music" as someone posted above...I've never done that, but give it a go!
