This link has ALL WoTLK 3.3.5a Add-ons from I believe it was Curse(?) back in the day.
I Will help Guide you through this process the best I can.
You will need 7-zip or Win-RAR ( I use 7-zip pure preference)
STEP 1 - Download the file (scan with what ever Anti-Virus you trust)
locate your download(s) folder and right click the file then select "Extract to..." this should put all necessary files into its own folder (you will be scrapping it later don't worry)
STEP 2 - Find your ASCENSION WOW folder, it should be under OS:C then "Program Files" click on Ascension Launcher your looking for the Client folder inside that you want to click on Interface
you should see an Addon folder that's what we want.
so your bar up top should look similar to this OS:C > Program Files > Ascension Launcher > resources > client > interface > AddOns
STEP 3 - Now lets circle back a bit to get the files in the folder we downloaded, from here we need to take all the files we have in here and move them into the AddOns folder.
So we need to go ahead and open the folder CTRL+A all files in there (you should see a bunch of folders like swater and _NPCScan etc...) Right Click on a folder select Copy.
Go back to the AddOns folder go inside then Right Click a random blank space until a Paste option is available and go ahead and Paste them in there.
FINAL STEP After all files are moved we can go ahead and shrink the tab with AddOns then go and launch the Game via the shortcut, load up a realm of your choosing In the Bottom Left Corner there should be a red button labeled AddOns go ahead and click that, you should see all the AddOns we just put in the folder there, now on the bar you should see a Box labeled Load Out of Date AddOns go ahead and make sure that box is checked.
Once that is all done ALT+TAB and you can go ahead and delete the folder from downloads (told you we would get back to this lol) and get back into your game and enjoy the new AddOns you have access to
Gatherer has to have the load out of date to work properly