As to where you should start, I don't know if anyone could tell you exactly, but it would probably be building a join/connect server. If you mean where you should start learning, then the first thing you need to know how to do is a packet resolver, but server side emulation is not necessarily easy.
If you wish to start from scratch, then the first thing you need to do is understand how the already existing client communicates to the gameserver, basically and generally if you perform an action on the client, the client will send a packet with information to the gameserver on a specific port, and after the gameserver has resolved the action, it sends the client a packet with the response. This is of course a lot more complicated and it depends on the game, some games crypt their packets, obfuscate them, some games have heartbeat protocols, etc. After understanding how the client and the server communicate is where the whole "emulation" thing comes in, that's where you have to reverse-engineer, resolve and write protocols that mimic the original gameserver.
How to start an emulator is a simple question with a not so simple answer, I guess start by analyzing the game and finding out the order of operations (launcher > login > game) and let the flow of the game direct you.
--
A bit on the personal side regarding your last lines,
I think you are confusing, or misinterpreting/misunderstanding, the programming community and specially the emulating community, no matter the country of origin; it's not about them being "selfish and lazy", people who can make emulators are usually, at the very least, half decent programmers and/or have wide knowledge on how things work, those things aren't free and both require dedication and time to get better. Not publishing all their work as open source doesn't mean they are selfish and not teaching you doesn't mean they are lazy, if anything, it's you who's being selfish/lazy, many people start learning on their own.
If you want some personal advice, do a hell lot more of research, I'm sure a good 10 minutes of googling and surfing will provide a wide number of sources, information and other goodies, and if there's not a lot of info in portuguese, then you're gonna have to work on your english first
Good luck