Using SSH Agent

SSH agent allows a user to enter their passphrase(s) for unlocking various SSH keys once at the start of a session to unlock the keys and from then on for the duration of the session the user no longer has to enter the pass phrase(s).
Conventionally setting up SSH agent for use is a bit of a pain as it has to be run before the user session is started.
 

Storing Passphrases in the Keychain

To store the passphrase for your default key in the Keychain open a Terminal and run:

ssh-add -K

And to store the passphrase for a different key run:

ssh-add -K /path/to/private/key/file

When prompted for your passphrase enter it and that is it.