Raso will be free to play for Everton from mid-February, after featuring in Olympic qualifiers for her country.
"It means so much to me to sign for Everton," she said. "I'm extremely excited to make the move to develop myself and continue my footballing journey at this amazing club.
"Everton is a world-class club. The facilities, staff and players are among the best and I'm proud to be able to join."