metamask-extension/docs/adding-new-networks.md

Adding Custom Networks

To add another network to our dropdown menu, make sure the following files are adjusted properly:

app/scripts/config.js
app/scripts/lib/buy-eth-url.js
app/scripts/lib/config-manager.js
ui/app/app.js
ui/app/components/buy-button-subview.js
ui/app/components/drop-menu-item.js
ui/app/components/network.js
ui/app/components/transaction-list-item.js
ui/app/config.js
ui/app/css/lib.css
ui/lib/account-link.js
ui/lib/explorer-link.js

You will need:

• The network ID
• An RPC Endpoint url
• An explorer link
• CSS for the display icon