How to code access to DLL method from 2 Winforms?

[Lou Arnold]

I am trying to structure my code in a better way than a pile of classes. I was going to use a DLL, but I am now stuck.

The code below represents parts of the Windows Forms application and part of a DLL.
I need to make methods of the AxerDataMgrClass available to the code in frmEnabledApps class and MainForm class.
How does one do that?

using System;
using System.Windows.Forms;
using nsCommonDLL;
namespace AccessTestForm1
{
	public partial class Form1 : Form
	{
		CommonDLLClass DEF = new CommonDLLClass();
		public Form1()
		{
			InitializeComponent();
		}
		private void Form1_Load(object sender, EventArgs e)
		{

		}
	}
}

using System;
using System.Collections.Generic;
using System.Windows.Forms;
using CD = nsCommonDLL.CommonDLLClass;

namespace AccessTestForm1
{
	public partial class CommonDLLTestForm2 : Form
	{
		public CommonDLLTestForm2()
		{
			InitializeComponent();
		}

		private void CommonDLLTestForm2_Load(object sender, EventArgs e)
		{
        		I need to access TMC.UpdateAppsLists() here.
		}
	}
}

using System;
namespace nsCommonDLL
{
	public class CommonDLLClass
	{
		public string ABC = "aBC";
		public string XYZ()
		{
			return "xyz";
		}
		private string QQQ = "QQQ";
	}
}