When you request an address, all the information is displayed in the next page, including the address. An email is also sent with this information. You need to check also the junk/spam folders. Sometimes the emails end up there.
If for any reason the email is lost, you can still find this information in the "Stamps exchanges" page: http://100stamps.club/stamps/progress
On this page you can find a list with your exchanges. If you click on the id, you will find there all the information, including the address where to send the stamps.