For applying for Residence, go to the website: https://www.comune.milano.it/servizi/residenza-cittadini-stranieri.
You will find all relevant information in Italian. A translation feature is also available.
The Municipality of Milano set up an all-digital, fully-tracked application platform, so you can do everything from home.
Choose The link: cambio di residenza per cittadini stranieri provenienti dall'estero o da altro comune italiano. You will land on an application platform and you will be able to register yourself (Registrati). Just provide your personal data and e-mail address, click on the confirmation e-mail and you're done!
Now you can access the application platform with your e-mail and password. The platform is made of several tabs each one with a topic and is context-responsive (according to your answers, it will require the relevant data and documents. You can also save your work for later, so you can gather the needed data and documents and fill the application correctly in batches.
You can even start filling in the application, save for later, and resume your work later on (e.g. if you have to retrieve or scan more data). Last but not least is some documents and data are not sufficient, the City Registry officers can allow you to integrate the documentation and information through the very same application form, so you don't lose the previous work.