Hi there and welcome Toby
The procedure to do this is as follows
Open the Kindle Fire folder (titled "Kindle") on your computer, and then open the Internal storage folder. Drag and drop your photos into the Photos folder or personal videos into the Movies folder on the computer.
Then double click them from there
What happens when you do this?
If pictures is empty Toby, then there is nothing there.
Where exactly are you seeing pictures on the Kindle?
Also, there is no additional money needed