1. Grab the `OptimismPortalProxy` address and, using the wallet that you want to have ETH on your Rollup, send that address a small amount of ETH on Goerli (0.1 or less is fine). It may take up to 5 minutes for that ETH to appear in your wallet on L2.
1. Grab the L1 bridge proxy contract address and, using the wallet that you want to have ETH on your Rollup, send that address a small amount of ETH on Goerli (0.1 or less is fine). It may take up to 5 minutes for that ETH to appear in your wallet on L2.
When building applications for use with your OP Stack, you can continue to use [the Optimism JavaScript SDK](https://sdk.optimism.io/).
The main difference is you need to provide some contract addresses to the `CrossDomainMessenger` because they aren't preconfigured.
## Contract addresses
### L1 contract addresses
The contract addresses are in `.../optimism/packages/contracts-bedrock/deployments/getting-started`, which you created when you deployed the L1 contracts.
| Contract name when creating `CrossDomainMessenger` | File with address |