To add the final approach you’ll want to following. I’ll add the steps below each image. Maybe a bit more explanation than needed, but this is also for any possible future readers that stumble upon this.
From the flights panel, make sure that you select both the arrival runway and the arrival. Then right below that click the select button to select the approach.
Next, you can click the label of the approach you want in the map or you can select it from the list on the left. Click the name of the approach to preview it on the map. Finally, click the Add to route button to insert the approach. I’m not sure you can filter for just the runway. It appears to show all runway that are tied to the selected approach.
The map should now look as follows. The reason for the purple dashed line is (the way I understood it) that the arrival ends in a ATC vector line (this would show up as a discontinuity in most flight management systems).