WordPress Multisite User Global Registration


I am new using WP Multisite and I have a network of sites. (e.g. site1, site2, site3)

My question: how can I make users when registering in the main site or subsites, to be registered automatically to all other sites, so they can be able to login globally to each one of these sites using the same username, email, password?

How can I achieve that and what plugins shall I use?

Thanks :slight_smile: