- Go to the desired Teams channel from which you want to add a new tab.
 - Click the plus (+) > select the existing app or website > select the desired app or website:
 - Once the app is selected click 
Set up a custom tab
. Making your changes, fill in the necessary details, and choose the content you want to display in the tab. - Once the setup is completed click 
Save
, and your new custom tab is created in your chosen Teams channel. 
