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.
Or you can watch these tutorial videos: