If you have run through my last Managed Instance blog post, you have a Managed Instance at your disposal. The PowerShell script for creating the network requirements also contains steps to create an Azure VM in a different subnet in the same VNet. Unless you have a site-to-site VPN or Express Route between your on-prem environment and Azure, you will use this VM to connect to your Managed Instance.
Install Management Studio on the Azure VM. To connect to your Managed Instance, you will need the host name for your Managed Instance. You can find the Managed Instance host name on the resource page for your Managed Instance in the Portal.
I think this migration story is a bit easier for DBAs than the old Azure SQL Database strategy of building dacpacs.