In MetaMask, click on the network name then click on `Custom RPC` in the drop-down list. Scroll down to the `New Network` section. Enter the above RPC URL. You don't need to add a port number to the end of the RPC URL. Enter the ChainID, Symbol and Nickname if you like. See the [MetaMask docs about how it uses the ChainID](https://metamask.github.io/metamask-docs/Main_Concepts/Sending_Transactions).