There is an easy assistant under Setup / Data migration when using Office 365 Admin Center. In this Tutorial, we are going over the process to configure an end point to support the transition from mailboxes located on Exchange Servers on-premises to Office 365.
Before starting this Tutorial, we configured the Hybrid configuration between Exchange Server organization and Office 365. After that, the first step is to open the Office 365 Admin Center, expand Setup, and click on Data migration. On the right side, click on Exchange
In the new page, click on Settings.
In the new blade, click on Add endpoint.
In the new blade, if the autodiscover is working properly, we can detect automatically by entering an e-mail from the on-premises that will be migrated, plus the admin credentials.
That would suffice to configure the endpoing, click on Close.
We can click on Settings and we will have the default values for the current endpoint that will be used on the future migrations.