Do i need to go to the associate raid prior to the raid and tell it what we are going to raid or just let it do it on its own
and before i start the raid should i delete the current
WoW/WTF/Accounts/AccountName/SavedVariables/GuildRaidSnapShot.lua
You don't have to do anything prior to the raid. You can delete the .lua before you login to start the raid, or you can purge all the screenshots in-game using one of the /grss commands (not too familiar with them unfortunately, it's probably /grss purge or something).
During the raid you can take snapshots manually or automatically, again using /grss commands. I believe it's set up to take snapshots on every boss kill by default, and records all the loot. You do all the messing around after the raid is over, uploading the .lua and what-have-you.
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**EDIT: So apparently I'm an idiot. Ignore what I said, here's what you need
http://www.dkpsystem.com/dynpage.php?id=17