The next step is to start up your client. In the folder you unzipped the Mekwars:Legends client to you will find a file titled startClient.bat (shown to the right). You will need to execute this file to begin the login process to the campaign. Its is recommended that you have at least 256K Ram available to run the mekwars and Megamek clients that will be running during the course of the campaign. 
It
may take a few moments to log in, when you successfully log in you will
see the server interface and a prompt to ask you to "get started" and
"register". Complete the prompts and you are ready to join the campaign!