The usual app creation process will create a service by default; you only need to follow this process if you're creating another component for your app that needs an internet-accessible endpoint. If you don't need this component to be internet-accessible, create a worker instead.
Select the source code for the Service on GitHub. If connecting for the first time, you will see an empty repository list and will need to click the link labeled Configure your GitHub permissions, then refresh this page.
Next, give the Service a name and select which branch of the source repo you'd like to use as the source of the Service. Click Next.
App Platform will inspect the code and select an appropriate runtime environment (such as Node, Ruby, etc). If you need to override this, you can see if there is a better options in the drop-down labeled Type as well. If nothing suitable appears there, upload a Dockerfile to your branch and restart the app creation process.
App Platform will also display any appropriate build and run commands that it detected, which you can now customize as needed.
If the use of environment variables is required, click Edit and supply them. Click the Encrypt checkbox to ensure a variable's value is obscured in all build, deploy, and application logs.
Select a plan, and click Launch Service.
Go to https://cloud.digitalocean.com/apps, click on your app, and click on the Components tab. Click the Service you'd like to edit.
Go to https://cloud.digitalocean.com/apps, click on your app, and click on the Components tab. Click on the Service you'd like to destroy.
You can destroy the Service by clicking the Destroy Component button on the bottom of the page and entering its name to confirm your selection.