Depending on which form creates the other, set up a public property in the created form which set to the DataSet and TableAdapter.
So, if Form1 create Form2, then Form2 has:
public DataSet dataToManipulate {get; set;}
public TableAdapter tableToManipulate {get; set;}
And Form1:
Form2 frm = new Form2();
frm.dataToManipulate = myDataSet;
frm.tableToManipulate = myTableAdapter;
frm.ShowDialog();