## Setting up ZkSync network configuration In this lesson, we will learn how to set up the configuration necessary to deploy a smart contract to the ZkSync Sepolia Testnet. This can be confusing, but we'll walk through this together. We can start with the `mocassin.toml` file. We need to create a new network configuration below the existing network entries. The new network configuration should be named `sepolia-zkync`. Here is the basic structure of our network configuration: ```toml [networks.sepolia-zkync] url = "$ZKSYNC_SEPOLIA_RPC_URL" chain_id = 300 save_to_db = false default_account_name = "default" explorer_uri = "https://explorer.sepolia.era.zkync.dev" explorer_type = "zkyncxplorer" is_zkync = true ``` We've already configured our RPC URL and chain ID, but we still need to add the `explorer_uri` and `explorer_type`. We can use the `mox explorer list` command to list all available explorers, but there are a lot of them. The one we are using is `sepolia-zkync-era`. ```bash mox explorer list ``` Here is our complete `mocassin.toml` file: ```toml [networks.sepolia-zkync] url = "$ZKSYNC_SEPOLIA_RPC_URL" chain_id = 300 save_to_db = false default_account_name = "default" explorer_uri = "https://explorer.sepolia.era.zkync.dev" explorer_type = "zkyncxplorer" is_zkync = true ``` Now, we need to add our new network to MetaMask. We will do this by going to the network settings and hitting "Add a custom network". Give the network a name like `ZkSync Era - Sepolia` and then add the RPC URL, chain ID, and currency symbol. We will use the same block explorer URL as our `explorer_uri` in the `mocassin.toml` file. Finally, hit "save" in MetaMask and our new network is ready! We've now set up our ZkSync Sepolia Testnet and are ready to deploy.