Very simple, the light that is on your trailer should have a metal ring around the lens.  Use a small flat screw driver and it pops right off.  Or if someone has updated them it will me a rubber mounted light, still use a small screw driver and work around the rubber edge and it will pull out.  This type light you have to replace the light, the other style you just replace the bulb with a 1157 bulb.

Or if you are around Ft.Worth/Decatur or Weatherford give me a call and I can show you how or do it for you.

HTB

Wal-Mart, Autozone or just about any parts store in town..  They are really easy to change out and has 1 plug on the back side of the housing.

Just don't get to rough when using the flat screw driver to pop it out.

Replacement lights are available at auto parts stores, RV/trailer suppliers, truck stops, Sears, Walmart etc.

Using a common screwdriver (straight slot) and by sliding it around the inside of the rubber flange, the light assembly will pop right out. Some lights have wiring sockets and a plug, some have twist type electrical connectors, some are butt spliced. Disconnect the old light from its present wiring, and connect the new one.

Take some Vaseline and smear a light coating around the inside flange of the rubber grommet. The new light is pushed into the rubber ring as far as possible by hand, and then by sliding the screwdriver around the other end of the ring, the whole light will snap into place. It's not at all difficult to replace.

gard