You will learn how to launch SyncThem calendars add-on from your Google Account
Launch SyncThemCalendars
From now on, you can launch our addon, from Gmail, Google Calendars or Google Sheets, by clicking on the right side bar icon as show below :
Click on SyncThemCalendars icon directly in Gmail or Google Calendars
The addon will open, and you can now create your first sync.
If after the installation, SyncThemCalendars icon doesn't appear in the side bar, you may need to refresh the page.
If after refreshing the page, the icon still doesn't appear, are you using multiple Google accounts under the same Chrome Profile ?
There is a limitation in Google Chrome, the simplest way to avoid it is to use the same Google account for the installation than the one you are logged in Google Chrome