How to insert/update information in SqlServer using C# : Hello I am trying to insert new information into my already created table where id = 2019;

I get the error incorrect syntax near WHERE

    private void button6_Click(object sender, EventArgs e)
    {
        xcon.Open();
        SqlDataAdapter xadapter = new SqlDataAdapter();
        xadapter.InsertCommand = new SqlCommand("INSERT into dbo.SysX VALUES (@fpp, @sdd, @sff) WHERE id = 2019", xcon);
        xadapter.InsertCommand.Parameters.Add("@fpp", SqlDbType.Int).Value = Convert.ToInt32(textBox1.Text);
        xadapter.InsertCommand.Parameters.Add("@sdd", SqlDbType.Int).Value = Convert.ToInt32(textBox2.Text);
        xadapter.InsertCommand.Parameters.Add("@sff", SqlDbType.Int).Value = Convert.ToInt32(textBox3.Text);
        xadapter.InsertCommand.ExecuteNonQuery();
        xcon.Close();
    }

How can I insert new information on click of button where ID = 2019

thanks