Copying on iPhone takes a tap and a hold. Here is the quick version.
Copy
Tap and hold a word, drag the handles to select what you want, then tap Copy. On this site, tapping a symbol copies it for you automatically.
Paste
Tap and hold where you want the text, then tap Paste.
Quick gestures
You can also pinch with three fingers to copy, and spread three fingers to paste, in apps that support it.
Facts to verify: the three-finger gestures on the current iOS version.