What exactly do you need help with? =o
If it's how to set your signature, simply click on your username at the top right, then you can see that there's a Signature text field there. Simply fill it with what you want as your signature.
If it's how to post an image, if you scroll down, there's already a guide on how to post it using the [ img=... ] tag (no space).
Hope that help. ^^