Just starting out, this may be a basic question, but I think I am missing something.

On Zoho Sites, I have a member portal, which they can login, with basic email info. Once in, I want a Customer Profile form, which enters the info into CRM.

How would I go about creating a form, such that when they log back in the second time, the Form is populated with their CRM contact data, that they can then update?

i.e. How do I link a Site's login to a CRM contact?

Second related question. I have a second module, which has a lookup to link it to the CRM contact. How do I create a form, that populates the lookup field, so that it links it to the contact that is logged in on the Site.