If you would like a signature you should do the following:

What is a signature?

A signature is either a picture or writing that goes under your post. That means every time you post , your signature will go in the bottom of your post.

To have a signature

Go to your profile.
Click on the word signature on the top right of your profile.
Once you add your signature, click "save"

Vwa-lah , you know have a signature.