PixelSugar's Files panel is how you browse your computer for images and select the image you're currently working on.
You can show or hide the Files panel with the grid icon above the panel
Choosing Images To Edit
Click an image to begin editing it.
Images that were previously edited have a black line under the image name (as in 007.jpg above)
Click on a folder to enter that folder. Use the back / forward buttons to to back or forward, just as in Finder.
Click the + / - icons in the panel toolbar to increase or decrease the size of the thumbnails.
Favorites
You can tag images as favorites, and then filter your Files view to show only favorite images. Hover your cursor over a thumbnail and a star icon will be revealed. Click it to add an image to your favorites. Click again to remove.
Click the star at the bottom of the panel to show only favorite images, and click again to show all images again.
Selecting Multiple Images / Batch Export
Use Cmd+Click or Shift+Click to select multiple images. Then begin an export. All your selected images will be exported.
At the moment, PxS doesn't support editing multiple images at once. Only the image shown in the Preview Panel will be modified if you edit the image.