How to redirect www with cloudflare

First of all, go to DNS settings

add www CNAME to root domain (you can specify @ and it will be replaced by domain after save), red fields are important:

Of course, replace imagetotext.app with your domain (this is an example).

Go to page rules:

Create a new one:

Again, replace imagetotext.app with your domain.

Force always using HTTPS

Another handy setting that is obviously a must is forcing HTTPS everywhere

Always use HTTPS: