If you want to learn more about Azure Cost Management to optimise spending in Azure, then have a look at the ACM YouTube channel. There’s a whole host of playlists, including a Quickstart one for a useful collection of short introductory videos. Find the channel here: http://bit.ly/2U55fA7.
Licence Reservation is a great way for EA customers to place mid-term orders for Online Services without a PO. If the prices are locked for the services, great, otherwise the QuickStart facility is there to order services before the price is locked.
This is a useful page on some of the most frequently asked questions on Licence Reservation and QuickStart: http://bit.ly/1xrQg1W.