Unfortunately, Friendica isn't well supported by the different mobile apps that exist for the fediverse. If you use Chrome or another Chromium-based browser (e.g. Vanadium, Vivaldi), you can do the following instead:

• Open friendica.au in your browser
• Find the option Add page to home screen
• Select Install

This will install friendica.au as a web app which behaves similar to a native app.

Play around with different theme settings (under Settings -> Display) to find the one that works best for your mobile device!