Just click on edit. You have to be logged in to do it. Once you make a change the ad will disappear into the approval queue for a moderator to approve for accuraccy and any potential scam issues. No sense in having us look at all these ads and approve them if someone could then immediately edit with scam info.
Pretty quick same day it's approved and back up, we look at them every couple hours.
If you have any problems just pm me the change you want and I will be happy to do it for you. Make sure to tell me exactly what the ad is for and in what section so I can find it.