Firstly, log into your WordPress installation. If you already have multiple sites, logging into any of them is ok.
In the top left you should see “My Sites” preceded with a key icon. Hovering over this with give you a menu, the first list item of which is “Network Admin”. The Network Admin is an important central hub in you multisite installation. It’s where you can create new sites, assign and install themes and plugins. Clicking “Network Admin” will take you to the Network Dashboard, which will appear similar to the normal WordPress Dashboard, but the menu on the left hand side will have different items.
It may be work checking whether your theme is installed first via “Themes”. If not, you may want to install your theme.
Creating a New Site
You’ll need a new site to develop with, which you can create via “Network Admin > Sites > Add New”. Enter a name for your site, and url, and add yourself as a user (so you can log in) and hit “Add Site”.
You should be presented with:
Site added. Visit Dashboard or Edit Site
Click “Edit Site” and navigate to “Themes”. Find the appropriate theme and click on “Enable” under the theme name.
The last thing to do, is to apply the theme to your newly created site. So you need to visit the dashboard of your site. You can do this via the “My Sites” Menu in the top left of your screen.
Once you’re in the Dashboard of the new site, go to “Appearance > Themes” and click enable on the appropriate theme.
You’re set to start making changes!
If you use the WP-SCSS plugin, you will now need to follow some extra instructions.