make ssl use diffie hellman

I want the server to use diffie hellman. So far I have figured out how to set the ciphers, the list of options is here. 
http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT

when I set the options to DH it didn't work, after talking with people it seems to need some parameters somewhere. For now the cipher is set to HIGH, which is the next best option.
