To add any Discord channel messages to your app, just add the channel_id as the source and set the data_type to discord.
This loader requires a Discord bot token with read messages access. To obtain the token, follow the instructions provided in this tutorial: How to Get a Discord Bot Token?.
import os
from embedchain import App

# add your discord "BOT" token
os.environ["DISCORD_TOKEN"] = "xxx"

app = App()

app.add("1177296711023075338", data_type="discord")

response = app.query("What is Joe saying about Elon Musk?")

print(response)
# Answer: Joe is saying "Elon Musk is a genius".