If you do not have a Datasource, click here.
Go to Contents. Click on the content that you want to use Datasource with.
Click the Code Editor button.
Click on the Media icon to the top right.
Click on the plus icon next to Datasource.
Choose the Datasource that you will use from the list.
Datasource will appear on the right panel. Now you can close the panel by clicking on code editor area.
Use the code editor to link your Datasource with content. You can get help from documentation here.
Request Approval, Approve and Go Live when you are ready to publish.