WordPress Multisite is a powerful tool that allows you to administer several WordPress websites from a single panel, including installing a specific theme on all the websites in the network.
- Log Into the Multisite Dashboard (www.example.com/wp-admin/network).
- Go to Themes > Add New.
- Click Install on the theme you want to install.
- Click Network Enable.
Now the theme is installed on all the websites, but you still need to activate it to use it.
- Now go into your website Dashboard (www.example.com/wp-admin).
- Click Appearance > Themes.
- Click Activate on the theme you’ve just installed.