Converting an existing Azure VM to a Reserved Instance

Solution 1:

All you have to do is to go to Azure Portal >> Navigate to All Services >> Reservations >> Click Add >> Define a scope and create.

You don't assign that reservation to specific VM, the discount is applied at the subscription level (or shared subscription level) automatically. See here:

https://docs.microsoft.com/en-us/azure/billing/billing-understand-vm-reservation-charges

And here's how you pay for it:

For Enterprise Agreement (EA) customers, Azure Monetary Commitment can be used to purchase Azure Reserved VM Instances. In scenarios where EA customers have used all of their monetary commitment, RIs can still be purchased, and those purchases will be invoiced on their next overage bill.

For customers purchasing via Azure.com, at the time of purchase, the credit card on file will be charged for the full upfront payment of the Azure Reserved Instances.