Open up your Outlook app
Click on File in the top left corner
Click on Option on the left
Click on Mail on the left column and then Signatures button on the right
Click New
Type a name for this Signature to label it and click OK
Click in the Edit signature box and type in the signature you want and then click save.
On the right for signatures you want to then mark the signature for New messages and Replies/forwards. Then click OK
Click OK