This guide will show you how to set a personal signature:
Firstly, in the Settings tab, select Signatures. From here you can click the 'New Signature' button:
The box shown in the image below displays what you will see next.:
Give your signature a name that can be distinguished from others you might create, then add your signature in the body section.
Once you're finished click save.
After doing this, your signature will show up when creating a new message:
This drop-down box will contain any signatures you create. This includes company wide signatures setup for use.