The Free Transform option can be accessed by right-clicking the canvas while using any selection tool. If you use it while an area is selected, only that area will be manipulated. If you don’t have anything selected, the whole layer is affected. Once in Free Transform mode, right-clicking again will bring up a new menu. Scale changes size throughout (click the linked chain icon at the top to keep the height and width relative), Skew (along with Distort and Perspective, but in different ways) will lengthen or shorten the edges of a selection, and Warp will bulge and constrain areas as you move the border frame.
Select layer Right-click anywhere on the canvas
Pull tabs Click your selection tool again and apply a transformation