Call method from main class in form.

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C#

I have very basic question, but I don't find the solution.
I have MAIN PROGRAM (maybee this is not a good name) and two form.
In this MAIN PROGRAM I call Form2. With button in Form2 I call Form1. Now I want to call method PS of MAIN PROGRAM with button in Form1


MAIN PROGRAM:

namespace Example.csproj
{
    public partial class SolidWorksMacro
    {

        public Form1 RWindow = new Form1();
        public Form2 BWindow = new Form2();
        

        public void Main()
        {
            BWindow.ShowDialog();
            
        }

        public void PS() 
        {
            MessageBox.Show("WORKING");
        }

        public SldWorks swApp;
    }
}

FORM2:

namespace Example.csproj
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Form1 frm = new Form1();
            frm.Show();
            this.Close();
            
        }
    }
}

FORM1:

namespace Example.csproj
{
    public partial class Form1 : Form
    {
        

        public Form1()
        {
            
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //I tried to call method PS with this two below sentence, but I get error: No overload for method 'SolidWorksMacro' takes '0' arguments

            //SolidWorksMacro m_Macro = new SolidWorksMacro();
            //m_Macro.PS();
            
            this.Close();
        }
    }
}

Therefore which is the best/simple way to call method PS with button from Form1.