On both iPhone and Android phones the app is usually updated automatically unless you have set your phone to require permission to update apps.

When Saphe launches a new update, it is usually first sent to a percentage of users, in the event of complications - not discovered during the test - occurs, then it won't affect all users at once. 

On iPhones, it is possible to download the latest update by finding the app in the App Store (https://apps.apple.com/uk/app/saphe-link/id1037858479?l=en) and downloading the latest update, even when the update has not been sent to all users yet. On Android, you have to wait for the Play Store to notify you that there is an update ready for the Saphe Link app.