You've started Emacs before you added your SSH keys to your keyring? No problem!
In the shell where you have your keys added to your keyring:
$ ssh-add -l
2048 SHA256:FPafasdfasf234 /home/torstein/.ssh/id_rsa (RSA)
256 SHA256:234124sdfsadf234234123 torstein@quanah (ED25519)
Get a hold of the values for these two variables that were set by the
ssy-agent
program:
$ set | grep ^SSH_
SSH_AGENT_PID=1315
SSH_AUTH_SOCK=/tmp/ssh-XXXXXX6O4ePc/agent.1306
Now, in Emacs, evaluate the following elisp:
(setenv "SSH_AGENT_PID" "1315")
(setenv "SSH_AUTH_SOCK" "/tmp/ssh-XXXXXX6O4ePc/agent.1306")
That's it. Everything in Emacs that uses SSH, like a typical Magit session, will use the same keyring that your shell uses.
Happy coding!