During cut scenes or regular gameplay, if your characters are supposed to talk, you will want them to move their mouth while they do so. Ideally, the lip movements match the audio from the voice line exactly. This is called lip syncing.
There are multiple approaches to accomplish lip syncing, depending on the level of detail you are aiming for. A very simple solution, for example, is to create just one single facial sequence that moves your character's jaw and lips a little for a few seconds to make it look like it is talking. And then you trigger this animation on a loop every time your character speaks.
Alternatively, you can manually create a facial sequence for each of your wave files in the Facial Editor. The next few lines show you the workflow for this approach.
First load a wave file into a sequence by navigating to Sequence | Load Sound. Then add phonemes by right-clicking on the Lip Sync track at the bottom of the timeline and choose Insert...