You can find the Registration form on the Social Networking Configurations page:
Click on the "Social Networking" tab, or the sub menu tab "Registration" to jump to this section.
Customize the Registration Form to ask the questions you want - with the format you want. Choose to make input fields text fields, menus (with the option of allowing user to select one option or multiple options), radio buttons, or checkboxes
Set Registration/Profile fields to be required or not. You can choose whether the form fields are to be used in the registration form, or the Edit Profile page only by checkmarking the "Profile Only" box for the field. If unchecked, the field will appear on both the Registration form and the Edit Profile page. Here you can also set the Privacy Options for each field, and the Default Privacy setting. Also, you can select whether a field is searchable by checkmarking the "Searchable" box. Checkmark the "Search Require" box to require a user to fill in the field in the member search form to perform a search.
The Privacy Settings section is farther down this page. You can jump to this section from the Social Networking sub menu tab "Profile" > "Privacy Settings".
In order to allow members to choose their Privacy Settings from their Edit Profile page (there will be a link there to load the Privacy Settings section to the page), you will need to set the "Use Privacy Settings" option to "Yes".