Use the Visual ODD Editor
Open the visual ODD editor by clicking on your newly created ODD on the start page. A new tab opens, showing an action panel to the left, and the title of your ODD to the right.
You can also use the visual editor to modify an ODD stored in a generated app outside TEI Publisher. Just pass an additional parameter root containing the path to the eXist collection in which your ODDs are stored:
We need to overwrite the processing model rules for dateline. Enter "dateline" into the input box next to the button in the left panel and click the button. This will insert a processing model rule for dateline into the right panel. Because dateline does exist in the base ODD, tei_simplePrint.odd, you'll already see a single model which was copied from the base ODD.
Expand the model by clicking on the arrow to the left of the grey box. A form appears, allowing you to change all relevant settings on this model. We would like to add an outputRendition, so click on the button next to Renditions. In the form input being inserted below, enter your css.
To test your change, click onin the left panel and wait a second until a popup appears. In your other tab, select the letter (make sure the correct ODD is selected) and view it.
The screencast below provides further information: