When addressing my email, how do I get my contact list to automatically enter the complete email address?

It normally does it automatically. Assuming the address is already in your contact list, usually by just typing the first couple of letters - you would get an option of addresses to choose and insert. However, for many people using Yahoo at the moment, the feature has a bug and auto isn't working. I reported it to Yahoo today and have just received this reply: "Thanks for writing to Yahoo! UK & Ireland Customer Care. I understand the Address auto-complete feature is not working in your Yahoo! Mail account. Thank you for taking the time to report this abnormal activity. I apologise for the inconvenience this is causing you. It is very unusual and looks like an unexpected bug activity. It has been reported to the engineers who will start working on it immediately. Please report back to us within 72 hours if there's no improvement. We appreciate for your continued support and apologise for any inconvenience caused." So it seems as if we have to wait for it to be fixed!