The voice actor gets the script and records their dialogue on mic in a studio, often with the help of a director and technical producer. Where voiceover gets complicated is in the details.

For a couple more examples of Dragonborn Voice Over in action, here it is with the Sith Inquisitor voice based on voice actor Xanthe Elbrick's performance, and below that are some of the lines ...

Assassin's Creed Shadows is based in Japan, but the script was written in English, and the Japanese voice actors have shared their thoughts on working on the game. In an IGN video, Mutsuki Iwanaka ...