Events + Meta references for the start date?

To set up Essential Grid with Events Plus (so that the grid displays in the order of event date instead of post date), Themepunch states that I need to create a "meta reference" for it so that it performs properly. They claim I can get the "meta value" for the start date with Events Plus, and use that to do it.

Simple question then: What is the meta value I'm looking for? Where ?

Thanks for your time,