Manage screenshots in bulk using project's Screenshots page.
All you need to do in most cases is drag and drop screenshot files (JPG, PNG, GIF) to the drop area. Lokalise will automatically recognize text on the screenshots and link uploaded screenshots to keys so they show up in the editor. In case the automatic tagging does not work, you can manually select keys/translations that are visible on the screenshot.
Optionally, you can upload screenshot to each key using the key editor.