First you open the app or device. (App is photo shown) Go to the settings button at the bottom and click on that.
Up will pop your information with a section called SEND TO EMAIL ADDRESS. Email your pdf to that address and you will then be able to read it on your Kindle. Sometimes I have found it will take several hours but it will come through as a document. Open the document on your Kindle as if it's a book and read it like any other book. (In the photo I've replaced my Email address with a phony one.)
Yup...that's all it takes...
Have a Great Summer Day!!