Log in to Service Center, go to Administration and add a new Database Connection. Enter the type of the database and server details and create the connection.
Next, create an extension to this database using OutSystems Integration Studio. You can use this extension in any OutSystems application.
This extension will now appear in Hubway Builder → Project → Entities tab as a module, and it will list all the Entities under it. You can select and add these Entities to your project.
Go to the Overview tab and click the Test link. You will see that the External Entity is listed like a normal OutSystems Entity, and you can perform the standard OData operations on it.