After his father had been slain by Vishnu in the form of the man-lion, he became, O Maitreya, the sovereign of the Daityas. And obtaining the splendours of royalty on account of piety, he came by immense wealth and was blessed, with a numerous progeny. At the expiration of the regal power and freed from the consequences of moral merit or demerit, he obtained, by virtue of his meditation of the deity final emancipation from future births.

In plain words: Later, after Vishnu killed his father in the form of the man-lion (Narasimha), Prahlada became king of the Daityas (demons). Because he was good, he ruled with great wealth and had many children. When his rule ended, through meditation on God, he gained final freedom from being born again.