How do the dead rise?
When? Definitively "at the last day," "at the end of the world." Indeed, the resurrection of the dead is closely associated with Christ's Parousia:
For the Lord himself will descend from heaven, with a cry of command, with the archangel's call, and with the sound of the trumpet of God. And the dead in Christ will rise first.
Source: Catechism of the Catholic Church (Vatican.va)