You mean MDI? or just you need to open Form2 from Form1 and use some values in Form1 user entered in Form2??
For second case, just create another Form let say it called Form2, some public members (TextBox, ListBox, etc...)
Add this code in Form1 to open Form2
Form2 form2 = new Form2();
fom2.ShowDialog();//enforces user to not back to form1 unless finishing work on form2
Get the value of form2's textbox
string str = form2.textbox2.Text;