Yahoo Mail does not offer a true email recall feature
You cannot unsend or retract an email after it has been sent
If the email was just sent, check whether you have an Undo Send option enabled
If Undo Send is available, click it immediately after sending
If the email was already delivered, send a follow-up email to correct or retract the message
If needed, ask the recipient to delete the email
For future emails, enable any available send delay or confirmation settings in Yahoo Mail