You need to import Unity's recorder package for use this editor.

you have to open "Multiple Screenshot Editor" on Unity Editor's tabs.

1. Click "Window" tab .

2. Click "Multiple Screenshot Editor" on "mr.yilanci" tab

3. You have to add device to the list. Click plus button for adding a new device resolution

4. Save your device resolution list as json to the project.  

Click "Save Json" Button. 

Resolution records are saved as json file in ....\Assets\mr.yilanci\Multiple Screenshot Editor.

5. Load your device resolution list as json from the project.

Click "Load Json" Button. 

Resolution records are loaded as json file from ....\Assets\mr.yilanci\Multiple Screenshot Editor.

6. You have to select where Save Screenshots. 

Click "Where Save SS" button and you can save want to where.

7. You have to play Unity for run the editor

8. Click "Take Screenshot" button . Time.scale be zero before the editor get screenshots for you saved device resolutions.

9.Time Scale is zero so time frozed . You have to "Time Scale 1" button for flow of time.

10. You can look the output folder by "Show Folder" button