Setting up a business directory

Hi, I am trying to get my head around the steps required to set up a searchable business directory similar to http://www.gran-canaria-info.com/index-old.shtml whereby users can add their own businesses and they are later searchable. I have trawled through the comments on this group and can't seem to find some step by step instructions. Can anyone point me in the right direction? If not could you give me some ideas to start,

thanks,

Richard