Sub-Models

I am building a reasonably large regional health model for renal services. To get around the lack of an array function I have created the top level model and then created a new module [sub-regional populations] with 4 sub-models, each populated with the relevant sub-regional data. However, I can't work out how to get data out of the sub-models or how to connect the sub-models to the top level model. As a result they just sit there as 4 independent models that I am unable to link in any way.  I'm obviously missing something. Any ideas anyone.

Thanks

David