Prerequisite: Knowledge of editing Data Entry Templates.
Navigate to Templates > Data Entry Templates, and select the template you want to edit.
On the DET editor screen in Standard Edition, look at the tabs you added to your DET.
On this screen there is a button that copies all fields over to the mobile version. Select Mobile Edition from the top and click the button.
Tip: Remember to add new fields to both Standard and Mobile DET Templates.
FAQ
Q: Do I have to have all the DET fields in Mobile? I don't need all of them on site.
A: You are able to reduce the number of fields you use on your mobile DET. Just select the Mobile Edition DET from the drop down, select the field you want to remove and use the arrow <- to move them out of the Tab under Fields.