If you want to use ssh key for login to our ssh environment instead your password, just follow these steps
0. Prepare your public ssh key (for putty example here)
1. login with your password to ssh environment.
2. Create file ~/.ssh/authorized_keys and put there you public key from step 0.
You can use just single command mcedit ~/.ssh/authorized_keys put there key and close, or if you prefer vim use vim ~/.ssh/authorized_keys
Don't use authorized_keys2. It is generated by our system and will be replace everytime you login.