Github puttygen.exe
I opened Puttygen and clicked the "Generate" button. I moved my cursor around to "generate some randomness". After the key was created, I entered a passphrase for the key and clicked "Save private key". I saved the file as "private.ppk" in the directory c:/Users/Kristen/.ssh.
Then I clicked "save public key" and saved the file as "public.pub" inside c:/Users/Kristen/.ssh.
Then I copied the contents of the field labeled "Public key for pasting into OpenSSH authorized_keys file". I did not copy the contents of the public.pub file, because I know that has extra data that will break the key.
I went to my GitHub account, went to Settings > SSH Keys, and clicked the "Add SSH key" button. I gave they key a title, then pasted in the key I copied from Puttygen and clicked "Add Key". The key was saved successfully.
I opened Pageant and clicked "Add Key". I selected the file "public.ppk" from c:/Users/Kristen/.ssh. I entered the passphrase.
Permission denied (publickey).
I saw that it was looking for id_rsa, so I created a directory named id_rsa and placed my keys inside it.
Enter passphrase for key c:/Users/Kristen/.ssh/id_rsa:
I entered the passphrase for my private key but it kept asking again and again.
Then I deleted that folder and changed the name of my private key to id_rsa.ppk, but got the same "Permission denied (publickey)" message.
I went into Control Panel > System > System Properties > Advanced > Environment Variables, and my GIT_SSH variable is set to c:\Program Files (x86)\PuTTY\plink.exe, and I confirmed that Plink does live in that folder.