Since the application is not available on the official website, you will have to work with it from your computer. To lower the file size of the images you can either:
Resize them to a lower resolution while keeping the quality.
Lower the resolution from 65 % (perfect for JPG) to ~50 %. This will lower the file size, but the quality will be 99.99 % the same.
Additionally, if you don't have the possibility to use the Lenovo Photo Master, install XnView and resize the pictures using the Batch processing feature as show in the image below:
Download XnView: http://www.xnview.com/en/