Step 1: download the smashladder version of dolphin from here https://www.smashladder.com/download/dolphin/Faster+Melee+5.8.7

Step 2: Once you have dolphin downloaded go to tools and click start netplay

Step 3: Once that window opens click the bar that says "direct connection" and set it to Traversal Server

Step 4: Download a Shrek Super Slam Iso from a Iso/Rom website (emuparadise)

Step 5: Once you've finished downloading shrek super slam click the spot on dolphin that says "Dolphin could not find any GameCube/Wii ISO's or WAD's. Double click here to set a game directory" and set the game directory to the folder your downloaded shrek super slam ISO to then press refresh in dolphin

Now its all set up