how to integrate one form from one project to required project

[watashi]

Mine is a mdi windows application.

i was already added that form in the required project in this way
right click on project name->add->addexisting Item
then i was selected that form from the location
the form was added but i was tryed to use that form in my application in this way

private void menuItem7_Click(object sender, System.EventArgs e)
{
Form1 objfrm = new Form1();
}

but it gives error in this way
ERRors:-
The type or namespace name 'Input' could not be found (are you missing a using directive or an assembly reference?)

In addition to adding the form (Form1.cs, Form1.designer.cs , Form1.resx) i also added the exe file using add refernce... .
But still failed.

Thnks in advance.