Before you can safely use an imported key, you need to sign it. To do so, issue the following command from your terminal:
If, for example, you wished to sign the key within the andy_oram_oreilly.asc file, you would need to obtain the username of that key. Let’s assume that the username is Andyo. You would then issue the following command:
gpg --edit-key "Andyo"
You will then be asked if you wish to really sign the key. As your reply, you need to provide the password for your private key. Once you do this, GPG will sign the key you have just imported.