From Pfäffikon SZ or Schwyz via the H8 to Rothenthurm.
Paid parking near the church.
Rothenthurm is very easy to reach by public transport.
The SBB/Südostbahn (SOB) runs every half hour from Zurich to Rothenthurm.
The "Voralpen-Express" (Romanshorn - Lucerne line) runs every hour from Eastern Switzerland and the Lucerne area to Rothenthurm.