In the latest version of the Downloader - a token to login is no longer needed. You may authenticate to link your catalog using your email address instead. It is recommended to start using the latest version.
If you still need a token to authenticate, use the steps below.
Make sure you are logged in to the NativeDSD Account you would like to connect with the app.
Go to Your Account > Downloader.
Below the steps to authenticate via email, can see the 'Advanced' dropdown. It looks this: ">Advanced: sign in with account token (legacy)".
If token is not showing a token, click on the button "Get a new token" on the same page within the foldout to generate it. The page will reload, please wait, and copy and paste it into the app.
The manual for the downloader app is available here.