How do I delete a lead, for example if someone asks me to remove their information?

Open the lead in Leads, tap “Delete this lead” at the bottom and confirm. Their details, message and your notes are removed and can’t be brought back, which is what you want when someone asks you to delete their information.

Only the owner and admins can delete leads. If you just want a lead out of the way, mark it Lost or tap Mark as spam instead; both keep the record.