So in C# to declare and instantiate a UserControl, you would go about it similar to this:
UserControl1 userCont = new UserControl1();
In vb.net it's quite similar, for a task pan (the panel at the right side of an office application) it is:
Dim userControl as UserControl Dim userTaskPane as Microsoft.office.tools.CustomTaskPane userControl = new UserControl userTaskPane = Me.CustomTaskPanes.Add(userControl, "Title") userTaskPane.visible = true
Now it should show the panel.
Edit: Source: https://msdn.microsoft.com/en-us/library/aa942846.aspx
Edit 2: You also need to set the right references. Assuming that you use visual studio, go to the solution explorer -> Your project -> References. In my project these contain the following:
I don't know if you need all of them, but for sure you will need some of them.