Look for the “link” icon, and tap it to enable link mode. In link mode phone numbers, addresses and web links in your draft will become links. Tap on a phone number to dial it, an address to look it up in maps, or a web link to open it in Safari.
You can also tap and hold on a link for additional options, such as "Add to contact" for a phone number, etc.
While in link mode, the draft is not editable.