How to install arcgis server ?

[tashi146]

Hi, I am new to arcgis, To create network layer for routing, I just install arcgis server from link and while installing I am getting following error.  

"Failed to create the site. The machine does not have a valid license. Please authorize ArcGIS Server by navigating to the Apps page and choose ArcGIS > Software Authorization."   

Question:   

1. Is arcgis paid ?

2. How to fix this issue?