Resizing an Imperial is incredibly easy to do and doesn't take long at all.
Here is a page you can print out to find the size that'll best fit you.
All you need is a little screwdriver and (potentially) a pair of scissors.
To make your Imperial larger: A little known fact is that you can technically make your Imperial slightly larger. All you need to do, is unscrew the aglets and then move them closer to the edge, as long as your screws can go into the fabric you shouldn't have any issues. By doing this you should be able to make it a tad larger which can make a huge difference in how comfortable it is for you.
To make your Imperial smaller: If you accidentally ordered the wrong size, or the small is too large on you, no need to worry. To make the Imperial smaller all you need to do is unscrew the aglets, measure out your wrist, figure out how much you will need to cut off of the Imperial, and then take a pair of scissors and carefully trim down the Imperial.
Tip: Make sure you cut evenly from both sides to help insure the name is still centered on the inside. Also, make sure to be careful how much you're cutting off. You don't want to cut too much off and have it be unwearable.