Tiwai is in southern Sierra Leone, reached by road and a short river crossing. From Freetown, most travellers drive via Bo and Potoru or Kambama; allow a full day because the later sections can be slow and rough.
Public transport is not practical for a short visit. Arrange a 4WD and driver through a local operator or the island management, and confirm the boat transfer before leaving town. In the rainy season, road conditions can change quickly.