Open the DJI app and configure the camera settings as desired. I have found on a sunny or bright day, the following settings give consistent results. Shutter priority (S), ISO 100, Speed 800, Aperture Auto. If available, you can also select Auto White Balance and and set the camera to AF (Auto Focus).
Close the DJI app completely (not just the window, make sure you quit completely out of the app if using an iPad)
Open DD and configure your Flight plan.
In the flight plan settings, open the Advanced tab
Make sure you uncheck "Automatic Camera Settings"
You should see this message on the screen as well, but if you have preconfigured the DJI settings per above, you can simply close the message window
DD will now use the custom settings you have set up in the DJI app.
FYI, setting the camera for Shutter priority and at least 800 (1/800 sec) in DJI assures that you will get consistently focused images, and that DJI will adjust the aperture as necessary to be sure there is adequate light for the camera speed.