1. Highlight the desired signature and long-press it.  Tap Copy.

2. Open the Outlook App on your device.  Tap the Green Button (#) in the upper-left.

3.  Tap the Gear Icon in the bottom left

4.  Tap the Signature Setting.

5.  Delete any signature there, then long-press the box and tap Paste.  Note: pictures cannot be pasted into the Outlook App's signature.

6.  This will paste in your copied signature.  You can slide up/down to double-check the accuracy.

Finally, tap the back arrow to save your changes.