On the Data Tables screen, select the desired data table by clicking it's name to add fields to it.
Figure 1 Table Name
This will show more details. From this view, click the Add new field button.
Figure 2 Add New Field
The Add New Field popup will open.
Enter a name for the field, in the Field name field.
Figure 3 Field Name
Use the Field Type dropdown menu to select the type of field you want to add.
Figure 4 Field Type
You can also add a new rule to the field by clicking the Add new rule + button.
Figure 5 Add New Rule
After entering all the required information, click the button.
Figure 6 Add Button
You can add additional fields by clicking the Add New Field button.
Figure 7 Add New Field
Once all the required fields are associated, go to the Details tab.
Figure 8 Details
To export the contents of the created app, click the button. The app's contents will be saved as a .zip file.
Figure 9 Export