http://uwb25d43nnzerbozmtviwn7unn7ku226tpsjyhy5n4st5cf3d4mtflqd.onion/posts/grapheneos/index.html
Both methods list the officially supported operating systems that you can install from. The first time you boot Graphene, it will ask you if you want to connect to Wi-Fi. Don't, we need to do hardware-based attestation first. Never set up fingerprint authentication.