You can Enhance any time, but it's not recommended. Food is a far more efficient way to level up and you want to save your mons, not use them up as feeders like in Heroes. Enhancing will have its purpose much later in your game.
Awakening requires two Megas. A base Mega at max friendship and any other random Mega as the partner. This will produce an Awakened egg in the Base digimon's digivolution tree. And it will inherit the leader and legacy skills of the Base. As well as any medals it has.