After downloading, you'll have to unzip the contents of the Web Part folder.
Note: If you have deployed the Web Parts on your SharePoint environment manually, move to the following section.
Each Web Part will contain the following structure:
To install the Teams add-on, we will need the contents inside the spfx folder:
── spfx 📁
└── Office365
└── SP2019
Click on Office365 and inside, you'll see a zipped folder containing the Teams add-on, that will allow for the installation inside Microsoft Teams.
Note: The contents inside the BT_webpartname MSTeams.zip should not be extracted, as the installation will require the zipped solution to be uploaded.