Once you have Outlook (outlook.office.com) open and are logged into it, click the gear icon in the top-right.
There are four categories on the left side of the Settings popup. Make sure 'Mail' is selected.
Once mail is selected, select 'Compose and reply' which is to the right and up from the 'Mail' category.
You should see two checkboxes. One says 'Automatically include my signature on new messages that I compose' and the other says 'Automatically include my signature on messages I forward or reply to'. Check both of these checkboxes.
There should be a box above those two checkboxes with a label above it that says 'Email signature'. Click into this box. This is where you will set your email signature.
