Create a signature (Outlook on the web)
Important: If you use both Outlook (the desktop application) and Outlook on the web, you need to create a signature in both places. See here for instructions on creating a signature for Outlook (desktop application).
Quick link to edit: https://outlook.office.com/owa/?path=/options/mailsignatures
1. Go to https://outlook.office.com/owa
2. On the top nav bar, choose Settings > Mail, which opens the Options panel on the left.
3. In the Options panel, under Mail, choose Layout > Email signature.
4. In the text box, type your signature and use the available formatting options to change its appearance. **Note: Inserting an image file (in a .gif or .jpg format for example) for your signature isn't supported, but you can copy an image from a webpage and paste it into the signature box.
5. If you want your signature to display at the bottom of all outgoing email messages, including replies and forwards, select the Automatically include my signature on new messages I compose check box. If you don’t select this option, you can manually add your signature to a selected message. See the next section for more information.
6. Select Save when you're done. **Note: You can always return to the Email signature page and select or clear the Automatically include my signature on new messages I compose check box.
Manually add a signature to a message
If you've created a signature, but didn't choose to automatically add it to all outgoing messages, you can add it later when you write an email message.
1. Go to your mailbox and create a new email message.
2. Type your message, and then choose More > Insert signature on the toolbar.
3. When your email message is ready, choose Send.
Edited from: https://support.office.com/en-us/article/create-and-add-an-email-signature-in-outlook-on-the-web-5ff9dcfd-d3f1-447b-b2e9-39f91b074ea3#bkmk_classic