On the Credentials page, in the Enter your on-premises account credentials section, select Use current Windows credentials ...

On the Credentials page, in the Enter your on-premises account credentials section, select Use current Windows credentials to have the wizard use the account with which you're logged in. If you want to specify a different set of credentials, unselect Use current Windows credentials and type the username and password of an Active Directory account you want to use. Whichever credentials you use, the account must be a member of the Enterprise Admins security group and have access to your on-premises Active Directory and Exchange 2016 servers.