The Chilean international, who has been described as "a very complete player" by the Spanish club's sporting director Miguel Torrecilla, joined Celta from O'Higgins at the end of last week.
"I'm very happy and grateful. I'm mentally and physically prepared for the league. When Celta called I didn't even have to think about it," he told reporters at a press conference.
"Celta is a great jump for me. The dream of every South American footballer is to be in the Spanish league. I'll try to keep up and offer my best version."
Hernandez will begin pre-season training with his new club next month.