Open Outlook and go to the File menu.

Select Options, near the bottom left of the Outlook screen.

In the Outlook Options window, click on Mail.

Click on the Signatures... button.

In the Signatures and Stationery dialog, click on New to create a new signature.

Enter a name for your signature and click OK.

In the editing area, type your signature text and format it as desired (you can include images, links, etc.). For example:

Set your new signature as the default for new messages and/or replies/forwards by selecting it from the dropdown menus.

Click OK to save your changes.

Close the Options window.

Your default signature should now be added to your emails in classic Outlook