You have several ways to go to Toyosu. I’ll introduce typical ways.
At first get on Keisei Electric railway then get off at Nippori station, “日暮里”. Change trains there. Get on JR Yamanote Line then get off at Yurakucho Station, “有楽町”. Next get on Tokyo Metro Yurakucho Line subway bound for Shinkiba, “新木場”. Then get of Toyosu station, “豊洲”. It takes around 90 minutes from Narita airport and costs about 2,800 Yen.
You can go to Toyosu by bus from Narita Airport. Get on Keisei bus bound for Shinonome, “東雲” or The Access Narita bus bound for Shinonome, “東雲”. Then get off at Shinonome which is the final stop. Shinonome is about 1 km away from Toyosu taking about 15 minutes on foot. It costs 1,000 Yen and takes about 2 hours. Several buses are bound for Tokyo station, “東京駅”. When you get off at Tokyo sutation please refer to the page “How to go to Toyosu from Tokyo station”.