1.1 - On the file downloaded from https://themeforest.net/ , it have a file called 'DEMO DATA'.
1.2 - You need to go DEMO DATA > Choose the Demo you want > Open file > Copy all data
You can use the Sublime Text to open file
2.1 - Go to Online Store > Theme > Actions > Edit code
2.2 - Open "setting_data.json" file > Paste all the data which copied from ''DEMO DATA' to here > click to 'SAVE'
Just support import config sections the same on demo, NOT support import images, products, data the same on demo.