After you registered your dApp via Dialect SDK, you'll be able to open Compose section in Creator Tools — dashboard.dialect.to.
Make sure to login in with the same key pair you used to set up the Subscribe Button
Fill the message for every channel: you could use the same message across all channels such as wallet, Telegram, email or SMS. Or you could modify the message to adapt to the specific medium. Then just click "Send" and that's it!