The former Palmeiras winger completed his move on Thursday.
He told the club's website: “I’m very happy to be signing with West Ham, a Club that trusted in my work.
“I also want to thank the (recruitment) team, who came to Brazil, not only talked with me but also with my family. They presented the project, and both my family and I liked it. So, I'm very happy to be signing with this Club and hope to contribute as much as possible. I also hope to win titles. If things go well, we have a beautiful journey ahead.
“When they arrived (in São Paulo), they showed me the training centre and explained what they wanted from me, not just from me but involving my family as well. They were enthusiastic, and I immediately wanted to come. I started discussing it with my family and representatives. Once again, I want to thank the team. They travelled from England to Brazil, and I’m very happy to have arrived.
“(The head coach and I) already had a conversation. He showed me his project and I believe I’ll learn a lot from him. He’s coached at the national level in Spain and managed big clubs. I’ve already started talking with him since arriving in London, and there’s much to come.
“From the beginning, they presented a project focused on winning. That was crucial for my decision because I love winning titles. Who doesn’t? I’m very happy to be here, and I’m eager to represent West Ham.”