An alternative for the .pem file issues;
1. From your Manage Server Screen, click Key Pair link.
2. Enter a desired keyname(variable) and click CREATE button.
3. Copy the Key Pairs contents. See below;
4. Open a notepad instance and paste the Key Pairs contents.
Save the file as (desiredfilename).txt
5. Open puttygen
From the menu, click Conversions -> Import key.
Browse for the .txt file that you created. And will look like this below;
6. Click “Save private key” button and click “Yes”.
7. Save file as .ppk (default extension) and your done.
Insert this file in the PUTTY->SSH-AUTH option.
Hope this one helps.