An onscreen magnifying glass helps you position the insertion point for typing and editing text. You can select text to cut, copy, and paste.
Touch and hold to bring up the magnifying glass, then drag to position the insertion point.

Tap the insertion point to display the selection buttons. Tap Select to select the adjacent word or tap Select All to select all text. When you’re typing, 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 grab points to select more or less text.

Select text, then tap Cut or Copy.

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.
Shake iPhone and tap Undo.