From the manual (imagine that):
Select text: Tap the insertion point to display the selection buttons. Tap Select to select the adjacent word or tap Select All to select all text. You can also double-tap to select a word. In read-only documents, such as webpages, or email or text messages you've received, touch and hold to select a word. Drag the grap points to select more or less text.
Cut or copy text: Select text, then tap Cut or Copy.
Paste text: Tap the insertion point and tap Paste. The last text that you cut or copied is inserted. Or select text and tap Paste to replace the text.