Bio Helmet Help?

Hi, I just have no clue how to do this:
I have made the Bio Helmet out of resin and all that good stuff and I have 2 sunglass lens that i would like to cut and shape into the shape of eyes to put into the bio helmet. But, I have no idea how to do so... Should I use a hair dryer to melt them in shape or should I cut them with a dremel or something? This is my first costume im working on so I need a bit of help.
Thanks in advance :)
Are your eye holes two separate holes? One big one? Do you have a pic of the bio? You may be better off using sheets of plastic (Clear folder from Officemax or Walmart works) with tint and/or netting (Window screen at Home Depot or black hose) behind it. All can be hot-glued. I would think that any heat you apply to the lenses is going to warp the vision, but if it's for display it may not matter. Don't think a hair dryer is going to be hot enough, though. You'll want to pick up a cheap heat gun at a place like Harbor Freight, Amazon, or eBay. Since you constructed your bio, I'm assuming a budget build. But if not, also look on Amazon and eBay for motorcycle helmet visors, paintball goggle visors, etc. Actually, look anyway, they're not that expensive.