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The Teams Meeting button in Outlook for Mac will appear in the Outlook for Mac ribbon if Outlook is running the correct production build and is activated with a Microsoft 365 or Office 365 client subscription. Check the below link to see which version your Outlook has to run. Check your Outlook to verify you have the correct or newer version. Check for updates by clicking Help -> Check for updates.
https://docs.microsoft.com/en-us/microsoftteams/teams-add-in-for-outlook#teams-meeting-add-in-in-outlook-for-mac
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Click "..." next to the team name then click as outlined by the numbers below
Share files in a Team / Channel
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