How do you water cypress trees?

No more than any other species of tree generally speaking. Cypress trees are often found in wet environments because they are very tolerant of them moreso than because they have a higher requirement for water. Cypress trees can make good lawn trees and in the absence of aquatic environments, usually don't grow the cypress "knees" that they are famous for. These knees are specialized roots that grow up above the water line to allow the tree to get sufficient air. As a side note, the most common reason trees die on construction sites is that too much dirt is placed around them and compacted and subsequently the tree roots aren't able to get the air they need to function.