how do i modify these two files plz ?

[sTeLLa]

plz explain,
whats an archive file ?
why wasnt the file i downloaded in the correct format?
which do i need to down load winace or winrar ?
then what happens to the file i down loaded, plz explain in simple terms, what i need to do exactly to make this file work i down loaded, once ive down loaded one of the above winrar or winace? do these programs do every thing for me etc ?

plz help,, many thanks