IEM is just another form of headphone monitoring. For recording I would strongly recommend standard headphones, as good IEMs are expensive and the cheaper ones aren't going to be as effective as similarly priced headphones.
Anyway, you just send a cue mix out of Apollo via cable to your IEM pack, like you would a standard headphone. So as long as you only need two to three monitor mixes, no additional gear needed (using Cue's 1 & 2 plus main output).