How to sidechain in Logic Pro?

I have just purchased Logic Pro and am happy to report quickly getting used to it, however I am experiencing one issue. I have been trying to sidechain a kick to a bass' compressor to create a throbbing sound. What Idid was set one of the ultrabeat sends to bus 1 and then chose bus 1 as the sidechain input on the es2 compressor. This has no effect and playing witht the settings does nothing. I have tried almost all of the other synths as well all to no avail. Any help would be much appreciated and if extra info is needed please ask for it.

-John-