How do I set a signature on the Samsung Seek for Boost Mobile?

I have the samsung seek and want to set a signature but don't know how. When u click messaging there's nothing that says settings. When u go to settings there's nothing that says messaging. So what do I do plz help.How do I set a signature on the Samsung Seek for Boost Mobile?I also have the Samsung Seek, and although ChaCha has an answer, the answer doesn't exactly work..

The most I have seen is that some phones don't have the text signature option, and this might be one of them.

dmv nc