He played an important role in fight against the emergency imposed by Indira Gandhi and was arrested in Bangalore. He was made Information and broadcasting minister when janata partry, a conglomerate of all major national parties barring communists, formed the govt in 1977. He continued as I&B minister till 1979.
The issue of dual membership resulted in the split of Janata party and those belonging to erstwhile Jan Sangh, including Advani, moved out and formed a new party- Bhartiya Janata Party.
Advani became the president of BJP in 1986 and introduced the concept of hard-line Hindutva as the core political ideology of the party. The rest, as we say, is history.