12/8 Time signature and note length coding

[David Johnson]

I'm working on an arrangement that is in 12/8 time signature and having 
trouble understanding how to encode note lengths and the associated 
chordmode timing.

Can anyone refer me to the proper place in documentation or even more 
helpful, list some examplesof how to show 1 chord for the duration of a 
12/8 measure?  I'm just not getting it from the documentation.

Many thanks,

David Johnson