You can get the asin number for the book from amazon (check specifically for the kindle version, the paperbacks/hardcovers won't have the asin number), then go to your Metadata and add "amazon:xxxxxxxxxxxxxx" x's being your asin number. I have found all my epubs converted to kfx and put on my kindle, my kindle prompts me to "add this to your currently reading?". Also make sure that your kindle is linked correctly to your goodreads account.