To make your characters talk, follow the instructions in these two short tutorials:
In addition, this article provides tips on how to get the best results.
Tip #1 - Don't use talking expressions when giving a voice to a character.
Why? Doing so will make the characters lips to move, even when the character isn't talking. This will cause the character to appear to be lip syncing incorrectly. Instead, either leave the Expression setting to Auto, or choose one that does not have a built-in talking motion.
Tip #2 - Assign voiceovers directly to a character, not to a scene.
To do this, click your character and select the Dialog tab under Character Settings, then add your voiceover.
Selecting the Narration tab & adding a voice to a Scene, as shown below, will not cause your character's mouth to move.