choose signature drop-down menu is grayed out

I know how to set up a signature for email; however, the "Choose Signature" drop-down menu is grayed out. I even put in several signatures thinking it needed more than one to choose from, but it is still grayed out. So I cannot choose a signature and thus my email does not have one.
+Choose Signature+
+Select a signature to appear in messages for the selected account. You can also choose to use all of the signatures in sequential or random order+
So that option does not appear to be available.

Any suggestions?