You’ll have to go to Sketch, select the particular updated artboards and sync to Overflow again. Screens that match artboard names will be replaced. Connectors to/from those screens will remain in place during the update unless the layers they started from were deleted in Sketch.
Learn more about syncing your Sketch designs to Overflow.
If you use Figma, then you'll need to import the updated frames to Overflow again.
If you use Adobe XD, then you'll need to sync your designs with Overflow.