This page describes how to import a signature created by GNOME Keysign.

So you have received an email with your signed key.

Technically, the attachment is an encrypted OpenPGP key. That key carries a signature from the signer. So you need to decrypt the key first and then import it. A gpg pipeline could look like this:

    gpg |  gpg --import

Use your mail client to save the attachment somewhere, e.g. /tmp/key.pgp. Then open a terminal and type

    cat /tmp/key.pgp |  gpg |  gpg --import

If everything works correctly, you should be able to read the lines:

gpg: encrypted with 4096-bit ELG-E key, ID AABBCCDD, created 2000-00-99
      "Foo Bar <foo@example.com>"
gpg: key AABBCCDD: "Foo Bar <foo@example.com>" 1 new signature
gpg: Total number processed: 1
gpg:         new signatures: 1
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0  valid:   1  signed:   1  trust: 0-, 0q, 0n, 0m, 0f, 1u
gpg: depth: 1  valid:   1  signed:   1  trust: 1-, 0q, 0n, 0m, 0f, 0u