To add a tab to a Teams channel, you will need to meet the requirements and follow the steps below:

1. Check your permissions: Ensure that you have the appropriate permissions to add tabs. If you don't, you will need to contact your Teams administrator for further guidance.
2. Access the Tabs page: Open the channel in the Microsoft Teams app, then click the ‘+’ icon next to the ‘Tabs’ heading to launch the Tabs page.
3. Choose your tab: Select the tab you wish to add from the available list, and hit the ‘Add’ button.
4. Authorize the tab: You may need to provide credentials and authorize the app as part of the setup.
5. Set your tab’s properties: If necessary, customize the tab name, visibility and other settings.
6. Click ‘Save’: Once you have configured your tab, hit ‘Save’ to add it to the channel.