Open PuttyGen, hit Generate, do NOT set a passphrase (unsafe!) if you intend to use it for rsync over ssh.
Copy the text from the authorized_keys box in PuTTyGen.
Put it on the server that you want to connect to.
in .ssh/authorized_keys
Save the public key. Keep it safe.
Save the Private key It should save as a .ppk. It's for PuTTy and WinSCP; so just keep it somewhere safe locally.
Click the Conversions menu, and hit “Export OpenSSH key”
Put it on the server you want to connect from in ~/.ssh/whatever
Open up ~/.ssh/config
Add in
IdentityFile ~/.ssh/whatever
chmod 600 ~/.ssh/config ~/.ssh/whatever