The Meganeura lived 300 million years ago,it lived where there was lots of oxygen and small prey that it could feed on.
The environment there was filled with insects and lots of trees.The meganeura would soar in the sky and snatch an insect and curl it in it feet and the when its dead it would eat it.The meganeura needed lots of oxygen today it wouldn't survive in our oxygen range.

To answer your question it lived in forests swamps etc.
other information about it is:
It lived during the Carboniferous era (the era before it created 40 meter tall ferns, which created massive forests and swamps and acted as huge oxygen pumps) due to extremely high oxygen levels megenuera, as well as many other animals at the time, to reach massive sizes.
It`s nickname is the queen of the forest.
It has a 3-foot wingspan and, like all dragonfly, is carnivorous.