Create Domain thats accessible from all pcs in network

Today i used my old computer to install windows server and I want to create a local website thats accesible from all PCs in this network. I already got it work that its accessible via the ip adress but I want to do it with an domain for example -> www.dropper.xy. I managed it to access the website on the windows server itself with the domain (changed the hosts file in the drivers/etc folder). I know i have to do it with some DNS stuff but i have literly no idea how. I hope you guys can help me out and tell me how to get this work.