Click on the "Admin" tab in the left sidebar

slack.com

If you are a business owner or manager, you may want to know how to add members to your Slack workspace in order to collaborate with colleagues, share information, and communicate more effectively. Adding members to your workspace can help you stay organized and ensure that everyone is on the same page. Additionally, it can help you keep track of tasks and projects, as well as provide a platform for team members to communicate with each other.

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