Editing list of permanent hosts in ssh. Remote X

[Antonio Rodr <arodriguez31@cfl.rr.com>]

1. 
Trying ssh from another woody computer I got the following:

The authenticity of host 'ip.here (ip.here.again)' can't be established.
RSA key fingerprint is se:qu:en:ce:of:nu:mb:er:s.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'ip.here' (RSA) to the list of known hosts.

Question: How do I edit it, since I don't want to have that ip left in the list?

2.
What must be done to enable remote X access?

Thanks to all.