can you describe in more details what exactly you want to accomplish?
(list) form creates/saves all its content to a list field on its own, as far as single form controls are connected to respective list fields. it doesn't need any extra create item action.
create item is a workflow action. within the action configuration dialog you have to provide a value for each list field you want to get populated.
the action however cannot access form, it can only access current list item fields, workflow variables or make a lookup to lists