The Italian defender has arrived from Atalanta, impressing in Serie A last season.
Okoli knows he will have to adjust to the Premier League, but is ready to attack the next challenge of his career.
“It’s amazing,” he told club media.
“I’m very happy and can’t wait to start. It is an incredible club. I’ve been here (in the UK) for a few days, so I’ve had time to settle. I’ve already met some players and the coach; I spoke a little bit with them. I was a little bit nervous but then I met them and I’m very happy now. They were all happy to see me.
“It will be a good pre-season; we have a lot of work. We have to start and know each other better. I think I’m quite a good and strong defender and I’m fast so hopefully I can bring more of that quality to this team. It’s a big step but with the team and the staff and the coach, they will help me to do my best.”