Open Active Directory Sites and Services from the start menu (Administrative tools)
Rename Default-First-Site-Name as required.
Right click on Sites and click New Site…
Give it a Name and select a site link object, click OK.
Right click on Subnets and click New Subnet…
Create Subnet objects for each sites.
Now go to Servers container. Right click and click Move… and select Site Name. Click OK
You can get site that a server belongs to by below command.
nltest /server:ServerName /dsgetsite