Domain Mapping with Wordpress Multisite

I've followed the wordpress instructions and installed/uploaded the domain mapping files and again, the option is now available in my dashboard, however I'm unsure about exactly what it is I need to do next.
I've added the ISP in the domain mapping configuration page (which is the same as my sites are all with the same hosting company), do I need to edit the DNS info or not as the new domain was purchased with my existing hosting company, If I do, what is it I am adding/changing?
Any help would be greatly appreciated as I think I'm 90% there and seem to be stuck at the last hurdle and would really like to get stuck into this new site over the weekend

EDIT - Or, should I just stick with a separate install for each site if i've only got a handful?
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