Since your question is very vague, I can but guess.
Anonymous cipher means, that the key exchange happens without any authentication taking please, meaning the no (server) certificate is used in the process. But without any authentication, the DH key exchange can easily be attacked by a MitM.
To mitigate this, you have to reconfigure your server software, whatever it may be. Look for the configuration setting where you can enter the allowed cipher suites. if you just want to get rid of the anonymous cipers, you must only disallow the
DH_ANON mechanism. Preferably it would be, to put in a whitelist of acceptable cipher suites.
A good guide for the specific settings of popular server software plus a list of acceptable cipher suites is provided by the friendly people of bettercrypto