Upon joining a server Ellie will DM you a link. Click on this link and you will be presented with the following page:
Check the "I'm not a robot" box and click continue. If everything goes alright you'll be greeted with this screen:
If you did not get a DM from Ellie, it might be because either your DM's are only open for friends - or you may have already been in the server.
If you were already in the server, and the server owner enabled verification. You most likely did not get the prompt. You can manually request for the DM by running this command:
If your DM's are closed you can either contact the server owner to manually verify you or you can change your privacy settings. You can always revert back to your original settings once you've verified.