1. Please log in to ebay Partner Network
using your email and password. Navigate to "Tools" > "Linkgenerator".
2. Select your program (e.g. ebay US), link-type: "Home Page" and provide a "Campaign Name" if not already set. Finally click "Generate Link".
3. In your "Preview" (blue text in screenshot) you can find the parameter &pub=XXXXXXXXXX (red underline in screenshot) - where the value of this parameter XXXXXXXXX is your Publisher-ID! This is the ID you have to save to affilitizer.