Mushroom Log

The other day I bought a mushroom log here in Renton WA. It’s about a foot long and covered with transparent plastic wrap. The inadequate instructions just say to cut the plastic wrap back, leaving it an inch beyond the log. Now what?

How can mushrooms grow when the log, except for the very end, is tightly covered? Doesn’t it need water? Dark or sunlight?

Amazingly, a group of oyster mushrooms is growing on the exposed end. Advice, please.