You must first ensure that you have the Metamask extension enabled in your browser and that the wallet you are using, has a valid NFT for the event you are attending.
Click the MetaMask button on the login page, and this will open your MetaMask wallet and ask you to connect to the site.
Once you have connected your MetaMask to the event, you may be required to add additional information, this is only if the specific event you are attending has opted to request more information and is not a requirement of BetterCast.