Get a big bucket that you can fit all or at least most of the sand in. Then go into the kitchen sink, bathtub, our outside by a garden hose and put the bucket with the sand in it in there. Pour water into the bucket until it's full, but leave room for your hands to go in without it overflowing. Start churning the sand with your hands until the water above the sand gets cloudy. Then tip the bucket slightly so the cloudy water starts to pour out, but the sand remains on the bottom of the bucket. If you're doing this inside, be VERY careful not to get much, if any sand down your drain or you might clog it up. Then just keep filling, churning, and pouring off water until the water is pretty clear after you churn it. Then go a few more rounds once you think it's clear enough, because it probably isn't quite yet.