You don't get one, you make one up! For each website, you think of a different Tracking ID to put on the links so you know from which site your hops are coming from
You conctruct your own tracking I.D... so if it was a link like: http://YOURID.olwcode.hop.clickbank.net/ and you added the numbers 123 in the tracking I.D. box...you would get http://YOURID.olwcode.hop.clickbank.net/?tid=123 this could be anything and you can put all different ones... like tracking ID = BLOG or =SITE or =HUBPAGES McrTech
after using TID, you will find [affiliate=YourClickbankNickname.TID] at the bottom of order pages. and you will find that under TID in your clickbank account transactions.