Press Community -> Profile. Log in to your Goodreads account. Once your account is linked there will be an "Account Transfer" button. Press that to download your library.
The Goodreads transfer page allows you to download the books logged in your Goodreads account to Book Crawler and, conversely, to upload the books stored in Book Crawler to Goodreads.
"Upload" allows you to select the books from your Book Crawler database to upload to Goodreads. "All" will upload your entire database. "Collection" allows you to upload books from the a specific collection. "Tag" allows you to upload books with a specific tag.
"Download" allows you to specify which shelf you would like to download from Goodreads. Shelves are translated to tags in Book Crawler. As an example, the "currently-reading" shelf will be downloaded and given the tag "currently-reading".
Press the action button to begin the transfer.