Creating an Interface for a WinForm Form to use DI

Question

I have a form that uses DI to access certain objects. I'm nopt sure how to inject the objects into a form's constructor. I'm sure I need an Interface for it but not sure how to create it.

Example: frmMain

private void tsmEncode_Click(object sender, EventArgs e)
{
    if (!FormIsActive("Encode"))
    {
        frmEncodeMessage message = new frmEncodeMessage()
        {
            MdiParent = this,
        };
        message.Show();
        message.Location = new Point(10, 10);
    }
}

Example: frmEncodeMessage

public partial class frmEncodeMessage : Form
{
    private readonly IWordBusiness _wordBusiness;
    private readonly ICodeBookDetailBusiness _codeBookDetailBusiness;

    public frmEncodeMessage(IWordBusiness wordBusiness, ICodeBookDetailBusiness codeBookDetailBusiness)
    {
        InitializeComponent();
        _wordBusiness = wordBusiness;
        _codeBookDetailBusiness = codeBookDetailBusiness;
    }
{