TS3 packages (the ones with the plumbbob on them) --
1. open up the sims 3 launcher
2. click on the downloaded file
3. it should be loading in the sims 3 launcher in the downloads section.
&
Package files --
I prefer just installing Delphy's Helper Monkey. Unfortunatley, it's unavailable on Mod The Sims. The link takes you to a site,which lets you download version 1.2.
I don't know if it's the newest one and if it actually works, but you can give it a try. I downloaded it in 2009, when it was on MTS & I think it's really good. A lot easier that extracting them into the Mods - Packages folder seperatley.
But if you do want to download them like that, I suggest checking out this tutorial: http://www.sims2wiki.info/wiki.php?title=Game_Help:Installing_Sims_3_Package_Files/Setup_and_Files
& the basics: http://www.sims2wiki.info/wiki.php?title=Game_Help:TS3_CC_Basics
