To change your signature in Outlook 365, open Outlook and select File > Options > Mail > Signatures. Click the New button to create a new signature, give it a name, and type or paste your desired signature text in the editor window. You can format the text using the available toolbar options (font, size, color, bold, italic, etc.) and insert images, links, or tables if needed. To set this signature as your default, select it from the dropdown menu under "Choose default signature" for new messages and replies. If you have multiple email accounts, you can assign different signatures to each account using the dropdown at the top of the signatures dialog. After customizing your signature, click Save and then OK to apply the changes. Your new signature will automatically appear on outgoing emails from that point forward.
For Outlook on the web (the browser version), the process is similar: click the Settings gear icon, select View all Outlook settings, navigate to Mail > Compose and reply, find the Email signature section, and enter your signature text. Changes save automatically. If you want to include HTML formatting or more complex designs in the web version, you can paste HTML code directly into the signature field. Remember that signatures apply to new messages and replies separately—you can set different signatures for each if desired.