Hi, sorry for not seeing this sooner. Basically what you need to do is go into your game right click on your assets folder in the file systems tab, go to the bottom where it says open in file manager and click on it. From there it will open a tab that looks like your files app, bring your actual files app up next to it, highlight the assets that you are looking to import and then drag and drop them into your assets folder.
If you need any more help let me know. :)