I don't use the Origin version of Sims 3. So I had to search this out. I'm not finding much, so I'm having to guess here.
From what I can tell the new Expansion/Stuff pack Launcher (1.69) is the same-ish as what you get with the disc version (1.67). Only the new launcher has the game selector with it.
Click image to see larger view
Copy your custom content = .Sims3Pack files into your Downloads folder.
C:\Users\<Username>\Documents\Electronic Arts\The Sims 3\Downloads
Open the Launcher, go to the Downloads tab, click Install All.
When it's finished, select the Installed Content tab. In this tab there should be a box you can checkmark - Run with Custom Content. To install your CC, click the Select All button. This may take several minutes depending on how much CC you have.
If you'd like to read more on the Expansion/Stuff pack launcher or if you are having problems seeing your cc, see any of the articles linked below.
Expansion and Stuff Pack Manager
https://sims3.crinrict.com/en/2015/11/expansion-and-stuff-pack-manager.htmlThe Sims™ 3 Expansion and Stuff Pack Manager
https://answers.ea.com/t5/Technical-Issues-PC/The-Sims-3-Expansion-and-Stuff-Pack-Manager/td-p/4937010The Sims 3 Expansion and Stuff Pack Manager
http://help.ea.com/en/article/new-launcher-for-the-sims-3/Hopefully this help. If it does, please let me know as I'm kind of curious if the launchers are still fairly similar.