How to Add the PUBKEY of this Repository?

[das]

Apt giving this error message for these two repositories, because I
don't have their gpg-key enabled. How to add that for these two
repositories:

W: GPG error: http://edevelop.org feisty Release: The following
signatures couldn't be verified because the public key is not available:
NO_PUBKEY 223020C2A7C6F0DF
W: GPG error: http://e17.dunnewind.net feisty Release: The following
signatures couldn't be verified because the public key is not available:
NO_PUBKEY 223020C2A7C6F0DF

Can someone please provide with the exact syntax, that I can copy and
paste, because I don't know the exact name of the keyserver of these two
repositories.