There are a few reasons that tubes look to be too large then the size they are made to fit. So first confirm the tube is the right marked size. Just because it was in the tire before does not mean it was the correct size. The tube should have the size (a diameter with a width range) either "inked' on it or moulded into it.

Assuming it started out being a suitable size... Deflate the tube to having only enough air in it to take a shape, not more because that makes the tube "grow' in size. You don't want a completely flat/devoid of any air tube as that will also make it look too big. (I explane this last point by referencing shopping for pants. When taken off the rack and placed against the legs the pants look too long. yet they some how "shorten up" when actually put on).

Most of the time either of these situations are the reason. However there is more. If the tire was ridden when the tube was too low in air pressure the tire tends to move around the rim. This will pull the tube along with the tire but the tube is held tight to the rim at one point, the valve. So the tube will stretch out on the side of the valve that the tire is creeping away from and bunch up on the side of the valve that the tire is '"working" towards. Often this is evident by the crease and floding on itself marks left on the tube.

So try my advice with only a touch of air in the tube first. If the tube still is too "long" to fit inside the tire without bunching don't fret. just replace the tube with a good one and go ride the bike. Life is too short to have the cost of a good tube holding you back. Andy.