not Rose

First i am very new to this whole mod process, and to make it worse im not the greatest with computers.

sorry in advance if this is the wrong forum to post this question...

with that out of the way...i want to play through the whole Baldur's gate series for the first time. i have installed a fresh copy of bg1, totsc, bg2soa, and tob.  I got the four in one disc set.  As per the mod instructions i chose custom with all boxes checked for the first two and full for the next two.  Next step i installed the two patches 5512 and 26498.  After doing some reading about the mods available i chose Baldur's gate trilogy.  The one i downloaded is bgt112.  Now my first dilemma, the read me instructed to extract BGT112-Install.rar to the BGII install directory.  Where can i find said directory (please, i know this is basic stuff...laugh all you want it wont hurt me, hehehe)?  When i installed the four discs originally i created a new folder for them

c:\baldurs gate\bg1 and
c:\baldurs gate\bg2

Any advise would be sweet...as i am sure this is the first of many questions to come

I dont think this matters but i downloaded all the mods i wanted to use from a mac to a flash drive, but i installed the game on my pc (no internet access)