If you have the images already saved with suitable file names, just Drag and Drop them all at once into FontCreator. PDF or AI files will be very much faster. Bitmaps should be big enough to give a good trace, but bigger images will be slower, of course.
Size Does Matter Do some thorough testing with the import threshold settings and decide how big the images need to be to get a smooth trace. Don’t bother creating hundreds or thousands of images that are next to useless for the required task.
Otherwise, try the method described in this tutorial.