Ok here is an update of what I have done in case someone has the same question:
1. The IPN v2.1 URL field in click bank I could not locate: I followed Cristian instructions: You automatically do not see the field once you click on Advanced tools in clickbank. You only see the Secret Key field. So you generate a secret key all in uppercase and save it then of course put that key to your wp dashboard area under your s2member options. Then copy the IPN v2.1 URL and go back to click bank. On the same place where you have the secret key, right below it says: " "Instant Notification URL: (request access)" You will want to click on "Request Access: It then opens up a page with a bunch of questions asking you whether you understand what each step mean. You must say yes. If you say no they will not approve it. If you are not so techie like me, you will have no clue what those questions mean but then you can trust the S2member developers as they have done all the work. So just answer yes to all the questions, accept to the terms and policy. Then click "Save changes and request API Access" Right away the field for your IPN v2.1 URL appears and Voila !! You just paste the link in there and save.
My other problem was with the Click Bank thank you page: Thanks to Cristian the answer is simple if you already have a click bank thank you page. Just link the s2mber thank you page url somewhere on your existing click bank thank you page that way the customer gets to the actual thank you page with whatever instructions you have and your contacts info etc.. and when they click on the Link to go to your member site or access your products, It is an actual link provided by s2member so everything is all configured.
Now on this stage I am still getting an error message when I click on the link on the thank you page even though I know I linked it right. So I decided to do a test purchase which is very easy to do with click bank. I used a different email to register on my own membership site as a level zero subscriber. Then I clicked on membership page to join did the whole test purchase and on thank you page, I clicked on the link to access my site but I got an error message. Clicked ok on it and was directed to the my page to log in. I used the same credentials I had created at level zero and despite the error message I was able to get access to the site's entire content at that point so it worked. On my site I only have Level one. About 10 minutes later I received an email saying " Thank you! You've been updated to:
One Time Membership Registration Of $67.99: Monthly membership at 29.99
Please log back in now to
http://www.....etc. "
So, I am all set just have to figure out why the Thank you page has a POST Vars error message but at least members are able to purchase and get access to the product.
Thanks Cristian for all your support.