Convert Putty key to SSH key

assuming you already have private key that was generated by puttygen, do following steps to import the key to ssh.

1. load the private key to puttygen with it's load function
2. in its conversions menu, choose export openssh. make sure format is ssh-2 rsa.
3. save the key to ~/.ssh/id_isa
3. with ssh-keygen, do
ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/id_rsa.pub