This post assumes that you have Windows 365 configured already and simply shows how to connect from an iOS device.
Firstly download the Remote Desktop Mobile app from the App Store – Remote Desktop Mobile on the App Store (apple.com)
Click the + icon in the top right hand corner and then “Add Workspace”. You need to then type in your Workspace URL.
To find your workspace URL go to https://windows365.microsoft.com and sign in as your Windows 365 licensed user.
Click the download icon on the left hand side
Then click Get subscription URL
Copy the URL and enter that into the Workspace app, then you’ll be asked to authenticate and your desktop should appear.
How to use Windows 365 on iOS