I'm assuming you are trying to set up an already authorized account with keys so you can stop using passwords. My answer may not be suitable or sufficient if you are doing penetration testing.
It appears that you have the purposes of the host keys and user keys for SSH mixed up. Host keys (those found in /etc/ssh) are for authenticating the server to the client. User keys (those found in your authorized_keys file) are for authenticating you to the server. So it looks like what you want is to provide public keys for your authorized_keys file. You may safely ignore the host keys for this purpose.
Out of the box, most systems expect you to generate a key pair on the device from which you are connecting to the server, and then either log in to the system with a password and transfer the public key to your ~/.ssh/authorized_keys file, or submit your public key to a service which installs the key on your behalf before you can log in. If you're using PuTTY or similar on a PC, use PuTTYgen to generate a key pair. On a Linux or other Unix system, use ssh-keygen.