First of all, please download and update to last free version of OrdaSoft Free Website builder
, there we fix small errors. So we will understand: we say about same version.
Please check, for add new field you need:
1. In OS CCK -> Layout manager, open or create "Add Instance" layout. This is important. The layout type must be "Add Instance", because in other layouts types, you may only use fields which you already created in "Add Instance" layout
2. There in left panel, under all fields which you already added, you see button "Add New", and please press it, so you will can add so many fields as you need.
Please check attachment image