Properly Scaling Pixel Art  

Go to the Move/Size/Rotate function. Select all frames and press Play.  

Use the Graph feature to easily animate your GIF. To enable Graph Mode, click the plus icon next to the timeline.  

Need to adjust resolution? Use Canvas Size in a separate small window.  
- If reducing resolution, first scale down your image using Scale All so it fits.  
- If increasing resolution, adjust Scale All afterward to upsize your image.