Clicking the main navigation link for Contacts, under the Suppliers & Purchases heading opens a list of individuals in a new tab in the main interface. These are the representatives of the suppliers you deal with, or wish to deal with - both suppliers & prospect suppliers can have contacts associated with them.
The list of contacts displays basic information and has various controls common to lists in Synergist, read more about common user interface controls in this article. Click on an item in the list to open the detail input form for that contact in a new tab in the main interface: