This anchor project illustrates one of the ways Callback VRF could be used. The source code is located in the solana-vrf repo under the https://github.com/orao-network organization.
It implements a basic Callback VRF client program that is capable of doing randomness requests and handling callbacks.
Invoke yarn install to install dependencies.
The guide is in the main main README.md.
You may also look into comments and code in the tests — they illustrates all the basic steps: client initialization, registration, funding and usage.
It comes with a CLI helper:
yarn run cli --helpPlease note that this contract is already deployed and registered for the "devnet" cluster,
so init and register cli subcommands will error. Also note that you can change contract id,
redeploy it on devnet and do all the steps manually.