This article explains how to use both the Skype for Business and Teams apps.
Please note that Islands mode might not be available for every Microsoft customer (or options from Microsoft side might change over time). In case below is not possible, please contact your Microsoft representative to check your options.
Starting Oct. 1, 2018, Microsoft Teams is the primary client for meetings and calling in Office 365. As Leddura 2Meet needs a Skype for Business account, here is how to use both the Skype for Business and Teams apps.
First, connect to the Teams and Skype administration center portal (https://admin.teams.microsoft.com) with an administrator account.
Then, click on Org-Wide settings, then Teams upgrade.
Finally, select Islands mode and Save.
If you'd like to know more, please read this article: https://support.microsoft.com/en-gb/help/4465277/microsoft-teams-now-the-primary-client-for-meetings-and-calling.