Doulos font help?

I looked online for a tutorial or some tips, but maybe someone here has a quicker answer than I could get by drudging through those for a quick question.

I am trying to transcribe with diacritics, and I can't quite figure out how to make sure my diacritics end up underneath the symbol that they're supposed to go with. How do I get that devoicing [o] thing to go underneath my [b]? When I insert it, it goes to the right of the [b]. Anybody?