The package files ? You don't need to open them. Just copy into your mods folder. If they are rar files you need to donload 7zip or winrar.
There was an update which caused my custom content not to work. Now, I can't copy and paste cc or mods. What is going on?
Please refer to this: http://help.ea.com/en/article/mods-and-the-sims-4-game-updates/
Whenever Sims 4 gets an update it takes out all of your custom content so that it can make sure that the update works on your computer. To prevent this, check on the Sims 4 site to see if there's any update, and if there is, than make a new folder for your cc, place it there, and play the game with a premade family for fifteen-twenty minutes. Then exit the game, put all of your cc back in (Left click and hold, and keep going down with your mouse until a blue box has covered all of your cc files. Then Right click, 'Cut' and paste them into your 'Mods' folder for the Sims 4).
And TA DA!
If you already started the game without taking out your cc and there's an update, stay chill and play for 10 minutes then exit. Take out all of your cc, make a new folder for your cc and put all the cc files there. Then play your game for 15-20 minutes, exit, and put them back in.
