Allow the phone app to remotely activate an available OTA update if they are not near the car and the car is in a safe mode for this.
The Tesla phone app gets a notification when an OTA update is ready. From the app, you can elect to install the update if the car is parked. Available in late 2018 with version 9.
(The comments saying otherwise are for older software that didn’t have the feature).
(voting combined from a close duplicate that has been removed)