You can get long evergreen garlands from the holiday section at Walmart. By adding real evergreen pieces you can make it look fuller and more expensive.
Start at one end and twist the end of the floral wire to the garland. Then, take pieces of the evergreens and wrap the wire around it, attaching it to the fake bough.
Work your way down the garland placing the evergreen pieces strategically to hide the wire. Cut the wire at the end and twist it around the garland to secure it.