Thanks again geekmaster, it worked like a charm.
For any other newbie kindlet developers out there with a Kindle 4 NT, I can confirm the following works to get a custom kindlet installed and working.
1. Jailbreak your Kindle are describe on the
Kindle4NTHacking wiki
2. Download a
kindlet to your PC. I took the kindlet named kapp.azw2 contained in the tar file
kapp.tar.bz2 from the "Guide: How to write a Kindlet" page as the source code is also there.
3. Copy the keystore file to your Kindle through USB. In kapp.tar.bz2 this is under the dist directory, named developer.keystore.
4. Copy the .azw2 file to the documents directory on your Kindle via USB
5. Connect to your Kindle using PuTTY and copy developer.keystore to /var/local/java/keystore/developer. You will find developer.keystore under /mnt/us after you copy it to your Kindle.
6. Restart you Kindle and you should see your application (in this case kapp) listed with your documents
7. Click on your application and it should load.
Hope this helps,
Ger