i bought sims3, but cant install late night.

hi, i think i have a special case here.
i bought sims 3 base, with a disc.
and now i want to play late night and medieval with the crack version i found in games4theworld.
so is it fine to just follow the sims3 mac guide by Dale with the "late night" part?
do i have to edit the terminal?
because i followed the steps for the late night part, until i cant open the installer at the dmg.
please advise
thank you.

You don't do anything to the base game, I have the original base game and it worked fine when I installed late night. Just install the base game normally, then follow the steps to install the Late Night expansion.

Usually when people have troubles opening the .dmg file, this is due to your extractor.. If you're not already, use the version of Stuffit expander that is in the guide and then this should sort this problem out.