OpenSSL certificates in Wildfire Server

Hello all,

some time ago I’'ve bought SSL certificate signed by private RSA key. My intention is to use this certificate in the Wildfire Jabber server but it seems there is some problem.

I have recognized from browsing off all the discussion topics on SSL here that I need also DSA private key. Am I right or is it possible to use certificate with RSA key ?

What is the purpose of using both keys ? SSL Guide is quite unclear on this topic.