Open Video Editor (it appears in the top menu when it is on for your account).
What you can do
Add your scenes to a timeline and put them in order.
Trim and split.
Add music, voice-over and subtitles.
Add text cards and effects.
Drop character cut-outs onto a place (Stage, beta).
Pick Simple layout to keep it easy, or Pro for more controls.
Export a finished video.
Step by step
Create a project, or open one from your projects.
Open the Scenes tab. Drag your scenes onto the timeline in order.
Trim: click a scene and drag its edges. Split where you want a cut.
Music. Open the Music tab, choose a track, and set its volume.
Narration and subtitles. Add a voice-over, or turn on captions.
Text cards. Add a title or a line between scenes.
Click Export. Upgrade to Pro to export. On Pro, choose your settings and wait for it to finish.
Tips
The editor saves as you go. Come back and keep working.
Build the order in Comic Lab first, then match it here.
Try Simple first.
Coming soon
Effect templates, scene moves and some effects are in testing and are not on for everyone.
Costs
Opening and editing are free. Upgrade to Pro to export. Making new scenes still uses credits.