"-nya" is a suffix that means "dia" (he/her/it). There is no exact word for "a" or "the" in Indonesian. The closest we have is "itu" (that) as Azlan999 mentioned.
EX: Buku itu berwarna merah. [The book is red]
If you put a pronoun/name in front of a noun, the pronoun/name is translated as the possessive form.
EX: Itu rumahnya. [That is his/her house] Itu rumah Ali. [That is Ali's house]