Instructions for iPhone:
The above video explains how save the web portal to the home screen of your iPhone.
This article from Apple also describes how to bookmark a website on your iPhone, and further down has the same instructions in the video for how to add a website icon to your home screen: https://support.apple.com/guide/iphone/bookmark-favorite-webpages-iph42ab2f3a7/ios
Instructions for Android:
The above video explains how save the web portal to the home screen of your Android.
To save the web portal to your Android home screen to use it like a mobile app, first open a web browser and go to app.rundna.com. Tap the three dots in the upper right corner of your screen and tap "Add to Home Screen." Navigate to your home screen and click on the new widget that has appeared. Log in with your credentials. From this point forward, you can can stay logged in and use the portal as if it were an app.