how can i use script builder ?

A script builder is not a scripting issue, it is actually a type of ROBLOX game that can differ greatly. I would suggest reposting this on the ROBLOX forums instead, someone there would probably be able to help you better there.

It depends which Script Builder you are attempting to use, there is a handful of options http://www.roblox.com/games/20279777/Voidacitys-Script-Builder-Working-Local http://www.roblox.com/games/21053279/redliuB-tpircS-cilbuP-sitnA (There is a couple more, but they aren't known/working)

Now you are probably going to want MakerModelLua's Script Builder bot https://dl.dropboxusercontent.com/u/55301310/Roblox%20Http%20Script%20Bot%202.exe (Shortened if you can't copy the first link: http://f.akk.li/MakerModelLuaScriptBot/ )

In the Script Builder there should be a "get/help" command, when you use it then it will show text in the 'Output' showing you how to use the Script Builder. MakerModelLua's Script Builder bot is customization with its settings, make sure it works with the Script Builder! The bot is pretty self explanatory...