I have downloaded the kindle app from Google Play Store and installed it.
I have some Kindle files downloaded from the internet. How can I open them using my kindle app?
If you have the Kindle app installed, just open it and it should show a selection of the books you've purchased from the Kindle store.
Books that haven't been downloaded to your device yet are available via the "Archived Items" menu option that pops up when you press your device's Menu, you should be able to select and download any books there.
If you've downloaded Kindle compatible books from elsewhere on the internet, then if you move them into the "Kindle" folder on your SD card, they should appear in the listing of books when you open the Kindle app.
You have two options to do this: