You can reach the temple in a 5-minute walk from either Enoshima Station (Enoden Line) or Shonan-Enoshima Station (Shonan Monorail). If you're coming from Kamakura, the Enoden ride itself takes about 23 minutes and runs close to the ocean and through narrow residential lanes, so it's a decent part of the trip.
The grounds spread across multiple levels, so give yourself more time than you think you'll need. The main hall dates to 1832 and the five-story pagoda to 1910, and they sit at different elevations connected by stairs. A stupa and a confinement cave tied to Nichiren are also on-site.
If Nichiren history is your focus, prioritize the former execution-site area and the cave.