To obtain their public key, import them from email they have sent to you and that includes it. Alternatively, you can try to discover their public key on a directory.
Akken ad d-tawiḍ tisura-nsen, kter-itent-id seg yimaylen i ak·am-d-uznen syen rnu-tent. Neɣ, ɛreḍ ad d-tafeḍ tisura-nsen tizuyaz ɣef ukaram.