Add generate key note

doc.zih.tu-dresden.de/docs/access/ssh_putty.md

@@ -35,6 +35,17 @@ You can pre-configure some connection details additionally. It will save time in
 
 -   Configure SSH-key (recommended for security reason).
 
+    ??? note "Generate your key pair"
+
+        If you do not have your SSH key pair (public and private keys) yet, you can generate
+        it using PuTTYgen program, which was installed together with the main PuTTY client.
+
+        ![PuTTY generate key pair](misc/putty8_gen_key.png)
+
+        Click on the button "Generate" to create a new key pair. Move the mouse pointer in the
+        respective field as requested. Afterwards save your public and private keys in separate
+        files. It is recommended to use a passphrase for a private key.
+
     To configure the SSH key to use, navigate to "Connection" → "SSH" → "Auth" in the tree left.
     You will see a text field for "Private key file for authentication".
     Insert the path to your local key-file or brows it using the button "Browse...".