When you add new tables or fields to your data source Stacker will pick these up the next time you run an update -- or automatically every 24 hours. However for the security of your data we will not enable any of these tables or fields in your app automatically. This means if you want to use any of the new tables or fields you've created you will need to manually enable them in Stacker.
After running a schema update in App settings, you can enable the table by expanding the arrow and toggling on the new table.
To enable a new field navigate App Settings and expand the datasource you have just added the new field in, click on the relevant table the field has been added in a toggle on that field.