[Andy]

A cylinder mapping is pretty simple. Imagine putting your object inside a tube which is a rolled up picture. Then the tube shrinks and wraps the object.

Select the surfaces you are having trouble with and look at it in the TCE.

You usually want to get each surface on the cylinder to have a different piece of the texture. Sometimes mapping can end up outside the main texture so you may need to adjust it so it's over the texture.

Perhaps post a pic of the TCE so we can get a better idea of the problem.