If you want affiliate to be redirected to ANY site after the signup, go to Merchant panel > Configuration > Affiliate signup > After signup subtab.
You can either write custom URL or use default web site - you can even edit the default web site template there by clicking Edit page template.
If you use default web site template: 'post_signup_page.tpl', you can use these widgets for displaying affiliate details:
Username: {widget id="username"}
First name: {widget id="firstname"}
Last name: {widget id="lastname"}
Affiliate referral ID: {widget id="refid"}
Parent user ID (system generated, not referral ID): {widget id="parentuserid"}
Notification email: {widget id="notificationemail"}
Data 1: {widget id="data1"}
Data 2: {widget id="data2"}
Data 3: {widget id="data3"}
Data 4: {widget id="data4"}
Data 5: {widget id="data5"}
Data 6: {widget id="data6"}
Data 7: {widget id="data7"}
Data 8: {widget id="data8"}
Data 9: {widget id="data9"}
Data 10: {widget id="data10"}
Data 11: {widget id="data11"}
Data 12: {widget id="data12"}
Data 13: {widget id="data13"}
Data 14: {widget id="data14"}
Data 15: {widget id="data15"}
Data 16: {widget id="data16"}
Data 17: {widget id="data17"}
Data 18: {widget id="data18"}
Data 19: {widget id="data19"}
Data 20: {widget id="data20"}
Data 21: {widget id="data21"}
Data 22: {widget id="data22"}
Data 23: {widget id="data23"}
Data 24: {widget id="data24"}
Data 25: {widget id="data25"}
Note I: Each widget can be used only once.
Note II: If you should need to add some kind of identification to the created element you can add class="whatYouNeed" to it - {widget id="data25" class="Data25ID"}