Could you provide me a guideline to use Network Key?

We can provide you with a brief guideline from start to finish.
Protecting Application
Use ElecKey Integrator (shell protection) or the KeyCheck API to protect your application. Please make sure that you set the application to detect the Network Key. The needed ElecKey system files include: EKC3220.DLL and the Network Key Agent NKAG20.EXE. The other thing is the Network Key Configuration file that specifies the NetKey License Server (NKLS) address, port number, etc. This is done for the protected application to be installed on a client machine.
Installing NetKey License Server
Simply run the NKLS setup installer on your server. You will then need to specify the configuration such as address, port number, etc. Note that NKLS only provides a TCP/IP communications for the application on the clients to access the Network Key on the server. The Network Key is installed separately from NKLS -- set the next step.
Preparing Register Utility for Network Key
In this step, you run ElecKey Integrator and choose the task to "Build End-User Utilities for Network Key". Please ensure that you assign the same Program ID as you did assign to your application. What you will get is the Register utility that allows you to install the Network Key on a server where NKLS is installed.
Installing and Licensing Network Key
On the NKLS server, run the Register utility for Network Key to install the Network Key on the server. If you have chosen to allow a trial period, the Network Key is ready without registration needed. Otherwise, a popup dialog with a Registration ID will show. To license it, run LicenseKey Manager. Enter the Registration ID in it, you can then specify the licensing properties including Max-User, etc. Click the Generate button, you will get a License Key. Back to the NKLS server, enter the License Key in the registration dialog. The Network Key is now licensed.
When you run the application, it connects to the NKLS. The NKLS checks the Network Key and use the properties such as Max-User to control concurrent users to access the Network Key.