Getting to Borobudur requires travelling from one of the nearby cities in Indonesia. There are many daily flights from Surabaya, Jakarta, and Semarang to Jogjakarta from which you can continue your trip by taxi or bus. Some flights are relatively short, such as the flight from Jakarta to Yogyakarta, which takes about 50 minutes. Once you are in Central Yogyakarta, Borobudur is 1-hour ride away. A private car for the journey should cost no more than 250,000 Rupiah, each way.
If you are feeling adventurous, you can take DAMRI buses from Jogjakarta to get there. It will be a 2-3 hours journey.