The lessons you are trying to download are in zip format, which is a very common file type on the internet. On most devices, all you need to do is double click the downloaded file and it will open.
Make sure you have a program for unzipping the files such as 7-zip.
If you have double-clicked it and it is not opening, kindly email us at support@deepenglish.com and answer the following questions:
1. What kind of device are your using?
2. What happens when you double-click the file? Do you see an error message? If so, what does it say?
It will also help if you can attach a screenshot of the error you are getting.