Help change the prefix site WPMU

Good morning, I just registered and wanted to know if I have to immediately pay for care enrollment. Then I write because I have a site in wp mu of siterground (http://vimado.it (the master domain) and http://friuli.vimado.it) and I need to ask your technical assitance for the following changes:
1) http://vimado.it -> http://www.vimado.it -> https://www.vimado.it
2) http://friuli.vimado.it -> https://friuli.vimado.it I wanted to know if you can help me? Thank you