How do I create and add a signature to emails in Outlook?

Avoid using images: Yes they may look pretty but they will increase your individual email size, not by much but multiple that by the thousands of messages and you're increasing your and your recipients' mailbox sizes unnecessarily.

Additionally a lot of email providers / programmes block showing images by default. Your recipient may therefore initially see a gap, a red cross or a banner asking to download the image instead of your lovely image.