Please download the MOBI version ebooks from the member https://member.rolandbal.com/
Once downloaded, send them to your Kindle email address. It's detailed https://www.amazon.com/gp/sendtokindle/email here.
An excerpt from https://www.amazon.com/gp/sendtokindle/email :
You and your approved contacts can send documents to your registered Kindle devices, free Kindle reading applications, and your Kindle Library in the Amazon Cloud by e-mailing them to your Send-to-Kindle e-mail address ([name]@kindle.com). Your Send-to-Kindle e-mail address is a unique e-mail address assigned to each of your Kindle devices and free Kindle reading applications upon registration.
Hope this helps. If you find any problem and need assistance, do contact us on support@rolandbal.com.