It is possible to connect datasets to a project directly from within the project page if you already have datasets that are owned by the same organization as the project.
The section "Connected datasets" shows a list of all connected datasets if any datasets have already been added to the project. A button to connect new datasets is located at the bottom of the table.
To remove the connection the trash icon in the connected datasets list can be used. This action must be confirmed in a pop-up window.