Purchase a new hose that is labeled "Safe to drink." If it is not labeled at all or if does not say, "Safe to drink," then do not buy it. Hoses without this label will contain too much lead to be safe for drinking water.
Put your 55 gallon water drum where you want it to store it. A single gallon of water weighs 8 pounds, so once your 55-gallon drum is filled, it will weight about 440 pounds. You're not going to want to relocate a 440 pound plastic drum.
Use a bung wrench to open the seal on your water barrel. Keep the wrench close; you will need it again to seal your water barrel back up when you're done.
Hook up your hose to water that is safe for drinking. Let the water run for at least three minutes to ensure it is clean, then fill up the barrel with the hose.
Add a bottle of water preserver concentrate. This is a solution scientifically tested and licensed by the Environmental Protection Agency to be mixed with your tap water that will make it continue to be safe to drink for the next five years. After you have poured the solution into the barrel, seal it back up with your bung wrench.