Or, get a vacuum sealer and put them in mason jars and seal the jar. If that is not an option, I would roll the bag up and expel as much air as possible, then put rubber bands or tape around it. THen I would put it in a freezer ziplock bag and do the same again. Then put it in the freezer.
Vac. Packing is the way to go though if you routinely have large amts. of hops on hand. I generally buy about 15-20lbs in 1 pound bags in the fall/winter and as I open the bags I put the rest in quart mason jars, seal them and keep them in the freezer. Opening and resealing as I need them.
Kegged/Serving: British Dark Mild, Oatmeal Amber, Pliny Clone, Porter, Bo-Pils, Oktoberfest, Stong Scotch Ale
Bottled: Barley Wine, Bourbon Barrel Porter
Primary: American Pale Ale, American Brown Ale, British Bitter
Secondary: Sour Cherry Stout, Sour Belgian Golden on Cherries, Bo-Pils, Belgian Strong Dark
Future Brews: British Dark Mild, German Alt, Porter, APA, American Brown Ale