It took me a YEAR to finally figure out how to load content from my computer into the Amazon Fire tablet I bought for myself as a reward for going through knee surgery last year. The old 8" one was easy, but this larger size would not talk to the computer. I was on the verge if buying a Samsung tablet so I could communicate with it better (instead of loading things with a thumb drive and the Amazon tablet explorer program). I did one more search and found the instructions about using the USB 3 speed cable and opening the access to the tablet from the top of the tablet screen/USB dialog (where it offers charging or other uses). Then the computer sees the whole insides of the tablet and things can be moved. I initially hacked the tablet to get some of the software I wanted and took some of it back out, thinking it was blocking access.

Amazon has a knowledge base/AWS site you log into separately to ask questions or participate, though you can read the site without logging in.