Ok.. Nabodita.. Here goes..
I tried this on my Paperwhite.. YMMV..
1. Copy pasted the following poem from:
http://www.poemhunter.com/poem/adhom-o-uttom/ into Gedit.. I work on Ubuntu Linux..
2. Saved above file as a text file..
3. Opened the text file in Calibre.. (you know about Calibre.. right..?)
4. Used Calibre's conversion function to generate .mobi and .azw3 files
5. Copied the .mobi file into my PW
6. Opened the .mobi file in PW.. It works.. So i'm sure the .azw3 should too..
I've attached all the files and a screenshot for good measure..
Hope you can take it further from here..
Enjoyyy..