The channels are used to alert the user.
You have several ways to review alerts. Via discord, telegrame or mail. By default, the email alert is configured with your login email address. If you want to use other chanels, your administrator will need to configure them.
To connect via discord, you will need to enter your user number (which you can find in the settings of the discord application). Once you have entered this number in the passive DNS application, a discord bot will contact you to verify your identity. You will need to re-enter the token given by the bot in the application. once this is done, you will be included in the passiv DNS group resseving alerts.
As you did for the discord part, you will need to enter your ID number in the application, a token will be given to you by a bot. Once this token has been entered in the application, you will be able to receive alerts on your telegram application.
As you have already created your account via your email address, you do not have to confirm your identity and therefore have not entered a token. In any case, you will receive an alert by email.