You can't. You have to get one from FireRed and trade it over.
Jynx cannot be found in Pokémon Emerald.
trade it
Yes, you can obtain a Jynx in Pokémon Emerald, but it is not available in the wild. To get a Jynx, you need to trade with someone who has it, as Jynx is exclusive to Pokémon FireRed and LeafGreen. Alternatively, you can evolve a Smoochum, which is obtainable through trading from those games.
You can only get a Jynx by trading from Fire Red/Leaf Green.
You can't catch smoochum you need to breed a jynx with a ditto to get it.
In Pokémon Emerald, Jynx can be found in the Safari Zone. Specifically, you need to go to the area known as the "Wetlands" during the "Pokémon" season. Keep in mind that Jynx has a low encounter rate, so you may need to use multiple steps and items to increase your chances of encountering it. Make sure to bring plenty of Safari Balls to catch it!
Get a jynx from Pokemon firered or leafgreen then put it in the daycare with a ditto and wait when you come back you can get an egg and when it hatches its smoochum. You can't catch smoochum you need to breed a jynx with a ditto to get it. Breed two jinx (leave in daycare)
Catch a load of Jynx and hire them out while you're asleep, beware, you may get a lot of BAD EGGs and the POKERUS.
No jynx does not evolve
jynx doesn't have an evolution
Jynx was created in 1996.
To nothing - Jynx doesn't have an evolution. You may be thinking of Smoochum, which evolves into Jynx.