Probably the best way to learn how to use a signal event is to look at the blog posts that Niall Commiski from Amis has written.
Oracle BPM 11g Signal Events and Oracle EDN – Part 1
Oracle BPM 11g Signal Events and Oracle EDN – Part 2
I doubt you'll find the documentation very helpful, but here it is: http://docs.oracle.com/cd/E28271_01/doc.1111/e15176/ipc_bpmpd.htm#BPMPD733
There are a few moving pieces to this, so you might need a little help if you run into an issue getting it to work. Ping the forum again if you run into problems getting it to work.
Hope this gets you going,