Hi there!
You'd need to sideload them. Find ES Explorer in the Amazon Appstore, and then connect your Kindle to your computer. It'll automatically become a drive which you can access using Windows Explorer. Open it, and drop the APKs:
Here's Aldiko
http://www.aldiko.com/download.html I'll go and get the free version of Mantano for you from Google Play.
Go into settings, and allow third-party sources applications to be installed (might be under security, I don't have my Kindle set up with the Amazon setup at the moment, but it's not hard to find
). After that, you'll want to disconnect the Kindle, open up ES Explorer, and find the files you added, click on it, and it'll ask you if you want to install them.
If you want me to, I can fix the fuzzy icons for you, some people like to use third-party launchers though.
EDIT: Glad you figured it out.
