as i read it you've google it but you can't apply it or make it there are plenty of guides and i suggest use the wiki of rathena and hercules but take note rathena and hercules are same emulator but the structures and codes of the both emulator are slightly different and i will suggest the you start with rathena.
il'l just type a follow through steps but this is note a complete guide but it will guide you step by step like linking please use search because your question might be answered
first download the rAthena Emulator, download you main client from here or from ratemyserver.net, Xampp for the database or mysql client, download tortoise svn or tortoise git, download notepad ++, then download a compatible client date like 2013 clients, download NEO patcher or any hexed patcher for client then start last download MS visual studio 2010 or 2012 to compile and edit your source files
first refer to rathena wiki
second use tortoise git or svn to download the emulator
edit the conf files using notepad++ (refer to wiki)
use xampp for you database or mysql client add and edit the login table to the ones you put in the conf file (refer to wiki)
after you edit compile using microsoft visual studio 2010 or 2012 run the server check if it has error (refer to wiki)
the if it has no console error then hex your own client or if your lazy enough you can download a precompiled client in the client section in rathena
the try your client and server
ps. i dont have time to make a guide and there a plenty of guides written by the members of the board
sorry for this reply but i just want to help
i may edit this to make a link in future i just don't have many free times now