I can't figure out what to do in the boss fight with the two women firing an emplaced gun from atop that one alien. I can't seem to do anything with the generator on the other side of the arena and I can't get close enough to the alien to do anything with it. 

There's a thing you can hit above you which will drop some rods which you may be able to use.

Simply put, knock the rods down. Run to the generator to the back of the room and hit the monster 3 times. It's really annoying especially with the finicky point and click.

As an addition to what OdinLin says, when you run back to the generator, click on it, and select the "Charge" option, then RUN on back to the boss.