What is the best way to preheat this insulated food warmer?

This is an online image of the type of container I have. I’m going to cook brisket and need it to stay warm while I transport it. What’s the best way to do this whilst avaoiding the meat getting too steamy or continuing to cook? Should I wrap the meat in foil etc. Any tips greatly appreciated!

Thank you!

by Pinapple_Mist-ery