。
My parents opposed my studying abroad.
Literal
Parents [topic-は] I [subject-が] study-abroad do [nominalizer-こと] [to-に] opposed.
~ことに反対する nominalizes the clause with こと and marks it with に as the target of opposition. 留学する (to study abroad) is a key vocabulary item for learners, as studying in Japan or abroad is a major theme.