This is one of the things I love most about WordPress multisite. It makes updating everything all at once really, really easy.
Plugins and themes can be updated as usual through the Updates page in the network dashboard as seen in the following screenshot. If you can't upgrade the WordPress core automatically, you probably can't update themes or plugins automatically, either. If that's the case, you can update plugins and themes manually just as you would on a regular WordPress installation; just copy the updated plugin or theme folder to wp-content/themes for themes, or wp-content/plugins for plugins. You can do this via FTP using FileZilla, or you can do it via SSH by downloading the updates, decompressing them, and copying the updated folders to their various destinations, as mentioned in the previous section.
Available Updates