Adding Angry SFX to my custom animation

It's actually a really easy process, once You get the sound name that You need as Leniad mentioned do the following:

1. Go to "Werehouse" tab inside Your clippack in Sims 4 studio
2. Click on Your clip that You want to add the sound event to
3. in the data tab of Your clip, go to "Events" & click on "Edit Items" that is next to it
4. Click on the "Sound" event on the left table
5. Paste the sound name that You copied from the list Leniad provided in the "SoundName" box
6. set the time code on when the sound should start playing, FE: 0.5 ; 1 ; 1.2 etc....
7. leave header1 & header 2 as they are
8. Click on "SuppressLypSync" event on the left box & click on remove "This will allow Your sim to lip sync to the sound"
9. Click "Save" on the bottom right

You'll have to do a couple more steps here now

1. You'll find a box called "IkTargets" 4 boxes below the "Events" box, Click on "Edit Items" of "IkTargets"
2. On the left box select "b__L_HandDangle_slot"
3. On the right box click on "IkChainIndex" & change the number to the amount of events You have in the "Events" box, in this case it's "1" if You added more than one sound count the number of events and put the number in the "IkChainIndex" box
4. Click "Save" on the bottom right

Save Your package & then close it & re-open it.

Now check the "Clip Header" of Your "Clip" & see if the events have changed there, if They have then Your good to go, if they haven't You'll have to re-do it manually repeating the last steps but for "Clip Header" this time.
Good luck

You're welcome  
Yes You can, I've added a lot of effects to My custom animations using "Sims 4 studio" & it worked perfectly. however You can't create custom "effects" yet.
check out this thread "sims4studio.com/thread/7407/help-effectevent" I explained how to add effects to Your custom animations ^^