1. The network designer is initiated by selecting Network Designer -> Load Network Designer as shown in the figure below:

A screen shot of the network designer is shown below.

2. The network designer has three important sections. These are "Devices
and Connectors" section, "Network Description" section, and the
"Network Diagram Design" section. Each of these sections are described
subsequently.
3. Working with the Designer:
1. Dragging and dropping devices and connections:
To include a device in
the network, simply click and drag the device into the work area. Release the
mouse after placing the device in the desired position.
On dropping the device you will be prompted to enter a Hostname of the device.
By default there will a Hostname typed in the input text area. If you want a
different Hostname then clear it and enter the hostname that you want to
assign for that device. You will also be asked to provide the ip address
information for the interfaces present. You may assign the ip address and
subnet information now or at a later time. It is optional. Similarly, to
connect two existing devices, drag appropriate connector into the work area.
Take the mouse onto the first device to which the connection is to be
provided. Drag the other end onto the device where the connection needs to be
terminated. During the process, you will be asked to provide the device
interface type and number (example S0, E0 etc.) for each end of the
connection.
2. How to configure a device:
On right mouse clicking a device, you get several options as shown in the figure.

Selecting "Configure Device" will lead to graphical interface
configuration menu. Here, you select the interface and enter corresponding ip
address and subnet mask. You can also exit without assigning and ip addresses.
Please note that the interface configuration can also be done in the network
simulator section of the program.

To establish a Connection between the two Devices, select the type of Connection from
available Connectors, drag and drop it on a device which has to be connected.
On doing so you will be prompted for the Interface to select for this Connection.
Select the interface and and click on Close button. Now the mouse point to the
other end of the connection. Drop the other end of the Connector on the other
device.
3. Display a device configuration data:
Selecting device properties
displays the current interface configuration details for the selected device
with respect to connected devices. A screen shot is shown below. It also shows
unconnected interfaces on a device.

4. Remove a connection:

As shown in the screen-shot, you can select the interface that needs to be
released of any connections.
This screen shows only the connected interface on a selected device.
Select the Interface and click on "Remove" to remove that Connection.
5. Remove a device:
By choosing this option, you can permanently remove a device and associated
connections from the network designer.