I have generated and downloaded a private .pem key from AWS. However, to use Putty in order to connect to the virtual machine, I must have that key in .ppk format. The process of conversion is detailed in roughly 20 lines here:

• http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/get-set-up-for-amazon-ec2.html#prepare-for-putty

I am using Linux Mint (an Ubuntu distro) and I know I can use puttygen in the terminal. However, I have no idea how to use this tool, nor how to configure the needed parameters. When I type puttygen --help I get

PuTTYgen unidentified build, Aug  7 2013 12:24:58
Usage: puttygen ( keyfile | -t type [ -b bits ] )
                [ -C comment ] [ -P ] [ -q ]
                [ -o output-keyfile ] [ -O type | -l | -L | -p ]
  -t    specify key type when generating (rsa, dsa, rsa1)
  -b    specify number of bits when generating key
  -C    change or specify key comment
  -P    change key passphrase
  -q    quiet: do not display progress bar
  -O    specify output type:
           private             output PuTTY private key format
           private-openssh     export OpenSSH private key
           private-sshcom      export ssh.com private key
           public              standard / ssh.com public key
           public-openssh      OpenSSH public key
           fingerprint         output the key fingerprint
  -o    specify output file
  -l    equivalent to `-O fingerprint'
  -L    equivalent to `-O public-openssh'
  -p    equivalent to `-O public'

But I have no idea whatsoever on how to do what the website tells me to do and all my tentatives failed so far.

How do I do what the website tells me to do, using puttygen on the terminal?