Do you have an ssh client already?
If not, then I recommend PuTTY, which is available here: http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
Download the putty.exe executable from that page.
To generate a key, get the puttygen.exe program too, and run it. It will give you some options for key generation, hopefully with sensible default values. if not, then a 2048 bit RSA SSH2 key is ok.
Save the private key somewhere. You’ll be given a public key too, which is safe to make public – specifically you need to email that to me.
Then I can add it here and then you will be able to connect using putty.exe to s0.barwen.ch
You will need to tell putty.exe to use the private key that you saved above.