There are many apps in the kindle store that say they will activate the camera on the Kindle Fire HD device, they might but you don’t need them.
When I first got the Kindle Fire HD, I couldn’t find the camera, well not in the device anyway. I went into the “photo” tab and could NOT find the camera icon. So i started testing it. I went into the Facebook app and took a picture from there, that worked. So I knew I could take pictures using the facebook app.
After downloading some photos. I went back into my “photos” tab and like magic there was the little camera icon at the top right.
So there it is. Try taking a photo through facebook or saving a photo from the web and the camera icon should appear in the photo’s tab. If i could take photos of the icon i would. That’s how I “activated it” by accident…like this blog post.