The Ecuadorian took a starring role for his country at this year’s World Cup in Brazil but understands it may take time to adapt to the physicality of the Premier League.
"I'm very happy to be part of this great Club and I'm hoping to do well. I'm going try to do my best,” Enner told the official site.
"I'm training normally at the moment. I'm training very hard and trying to get match fit. I could be OK for the first or second game. I'm not quite sure yet, that's up to the manager.
"It was a dream come true to score three goals at a World Cup. It's not something that happens every day. It was massive for my career and after that a lot of Clubs showed an interest in me. But thanks to West Ham, it happened.
"I want to repay the investment the Club have made in me. I appreciate the welcome that all the West Ham fans have shown me and hopefully I'll produce my best."