The following tutorial steps through the process of how to create your email signature and manually insert your signature into a message through Office 365 Outlook Web App.
On the top right of the page, click on the Gear icon and under My app settings select Mail.
In the Options menu, select Email signature and enter your signature in the text box. It is important to select Save after creating your signature.
*Note: At this step you have the option to choose if your signature appears on new messages, messages you reply or forward, or select both check boxes for the signature to appear on all outgoing emails.
You can also manually place your signature within a single mail item (this is particularly helpful if you utilize multiple signatures). Within a message, click the More commands icon and select Insert signature. The signature will insert in the message below your cursor.