To transfer eBooks to Kindle using Calibre, you first need to install the software on your device.If the eBook is in a supported format like MOBI, azw3, or PDF, you can directly use it without conversion.If the eBook is in EPUB format, you can convert it to MOBI or azw3 using Calibre.After importing the eBook to Calibre and converting it if necessary, you can send it to your Kindle device using the 'Send to device' button.