You should be getting more than a couple Spanish stations. ABC, CBS, NBC, CW, FOX are all broadcast near Las Vegas.
Check this
site for stations in the LV area and their locations. Use your location as guide and point to the locations on the map...see John from Detroit's post for quick reference for pointing. Do a rescan on your tv or digital converter to map the stations in view.
As far as a booster/amplifier is concerned, if you have a Sensor 4 Winegard batwing antenna, you should already have an amplifier either built into to the antenna or at one of your antenna connections. Adding another will not gain you much (there must be a signal present to amplify it).
There should be a small switch and associated power light showing it is turned on. Have you checked or seen this?
.