Rather important-Expanding BBsak
 

My question is so banal as to be stupid. I need a wiser user to assist.
I used "The Unarchiver" software program on BBsak.msi . It supplies a folder containing a number of plain text file and a *.exe file. I am using an iBook G4 running 10.5.8 .
How do I get BBsak functional? Step by step instructions, please.
Thanks for your help.