Once you are done generating it place <your-family-name>.key and <your-family-name>.crt in the <ip2ddata>/family folder (for example ~/.i2pd/family).
If you want to register your family and let the I2P network recognize it, create a pull request for your .crt file into contrib/certificate/family.
Certificates added into the public repository this way will appear in i2pd and I2P next releases packages. Don't place .key file, it must be shared between you family members only.
Run i2pd with the parameters 'family=<your-family-name>', and make sure you have <your-family-name>.key and <your-family-name>.crt in your 'family' folder.
Now go to Java i2p console http://127.0.0.1:7657/configfamily page and Join Existing Router Family selecting the file your-family-name.secret to join that family.
([source](http://zzz.i2p/topics/3313))
Export to i2pd from Java-I2P
----------------------------
Go to Java i2p console http://127.0.0.1:7657/configfamily page and export family key. You'll have a file `family-your-family-name-secret.crt`. It contains both the private key and the public key certificate.
Copy it to `your-family-name.key` and `your-family-name.crt`.
Edit `your-family-name.key` in a text editor to remove the certificate part so it contains only the private key part.
Edit `your-family-name.crt` in a text editor to remove the private key part so it contains only the certificate part.
Move the `your-family-name.key` and `your-family-name.crt` files to the i2pd /certificates/family/ folder, as instructed [here](https://i2pd.readthedocs.io/en/latest/user-guide/family/).
This assumes that i2pd/openssl can handle the PKCS#8 format for the private key.