Webhooks
A webhook is a channel-specific posting link. Pokkan uses that link to send the message you built. For this workflow, you do not need to create a Discord application or install a bot.
The webhook has a name and avatar managed in Discord. Its destination channel is chosen there too. Keep the entire URL private: possession of the link grants the ability to use it.
A bot is different. It can respond to interactions when its application implements that behavior. A button that opens a website is a link; a button that expects a custom action needs something to handle that action. Pokkan’s current Send flow does not supply that handler.
Start with Create a webhook, then Send your message.
Official references: Webhook introduction · Webhook API.