Ok so here is how Mera fits into the Arrowverse.
Mera, the wife of Arthur Curry and the Queen of Atlantis. After the death of her husband at the hands of Black Manta. Unable to continue on being the queen she appoints Tula to watch over the throne. Mera needs to strike out on her own, find her own path besides being the queen of Atlantis. She hears of a group of heroes, told although history, a woman leader, a woman with wings, a woman that can be any animal, and a woman controlling wind. Mera decides that she needs to find these women learn there ways as heroes. She winds up in Starling city and demands to speak to the hero going by the name of Green Arrow. The police and swat try to bring her in but Mera easily avoids them, as she continues to beat on the police she asks who is in charge of her attackers and Quinton Lance steps forward, Mera slowly begins to pull the water from his body and she asks again to speak to the Green Arrow. Suddenly a arrow shoots through the air grazing her shoulder ripping her scaly suit. He announces that she has gotten his attention and to let Quinton go. Mera complies returning the moisture to Lance. Creating a dagger out of the moisture in the air she walks toward the arrow wielding hero. She tells him that she comes in peace but will not hesitate to kill if she is attacked. She explains that she is the Queen of Atlantis and wife of Aquaman a hero that many had heard of. She tells arrow everything knowing that he has communication with this group of traveling heroes. Eventually trusting her he takes her back to the Arrow cave where she meets Black Canary and Felicity, she asks them if they to are heroes to this world, they tell her in a way but they are seen as vigilantes, working outside the law. Mera explains she is looking for the team of heroes led by a woman, Laurel smiles and tells her that that is her sister. They then call Sara and tell her about this water wielding woman looking for her. Sara being curious but cautious agrees to meet with her.
Mera, Canon in the dc universe but I guess OC in the Arrowverse, my fc is the beautiful Amber Heard and my password is Livewire.