Tulamben is on the northeast coast of Bali, roughly 90 kilometres from Denpasar and about two hours by road. Most visitors arrive by private car or scooter — there is no direct tourist shuttle from Kuta or Seminyak, though some Amed-bound services stop at Tulamben if you ask.
The road from Denpasar goes via Amlapura and around the base of Mount Agung, which makes for a scenic drive through rice terraces and volcanic landscape. Coming from Ubud, the drive is about 1.5 hours via the northern route through Kintamani and along the caldera rim — a worthwhile route in its own right.
If you are arriving from Lombok or the Gili Islands, the fastest route is by fast boat to Amed (some services) or Padang Bai, then by road.