Stuck clutch? This might help.
Quite a few clutches will not release when the engines come out of the box. Remove the spark plug and then install the chain over the sprocket. The included spark plug removal socket can be used to turn the clutch shaft. With the chain cut to length, installed, and master link installed replace the clutch cover. Re-install the spark plug to restore compression.
Move the clutch lever arm as far as possible to release the clutch. A good yank or two on the bicycle’s wheel will normally free the clutch. It’s a good idea to re-gap the spark plug at while doing this. Most are improperly gapped at the factory.
If the clutch still won’t release, remove the clutch plate. A couple of swipes with a round file on the inside of the holes, or drilling the holes out 1/16” larger would then work. Sometimes the clutch plate will seize up again before it’s worn in. The clutch lever will need to be pulled in and the wheel be given another yank to free it up.