Once Slack has been connected to Windmill, your team will have the ability to decide what channels Windmill has access to.
You can always check if Windmill is in a channel by clicking "View All Members" and selecting "Integrations".
Windmill does not have access to channels unless the Windmill app is added. Within Settings, you can have Windmill auto-join public channels to save the hassle of adding it manually (this is our most popular setting).
Windmill does not have access to DMs - your DMs are private.
Windmill does not have access to Private channels, unless the Windmill app is added directly to the channel.