One of the questions I'm most frequently asked in the shop is how to use the traditional Japanese ring type thimbles ( called yubinuki in Japanese) The 'correct' answer is that it goes on your middle finger between the second and third knuckle and is used to push the needle through like this:*
But I think the best answer is that because they are so flexible you can use them however it suits your own stitching style. We have quite a few different types in the shop at the moment - including some old handstitched 'kaga yubinuki'. I particulary like the leather ones because they are soft and flexible. I often find customers with arthritis like them because they can fit over knobbly fingers. You can replace the thread if you want to make them looser.
Here are some old thimbles from my collection. They have traditionally been made from tiny remnants of kimono fabric and silk thread. Some are just a simple piece of fabric stitched over a paper core, others are very finely and beautifully embroidered.
These last few (as well as others in the previous photos) are 'Kaga yubinuki' and feature this distinctive style of all over stitching which originated in Kaga (the old name for an area centred in Kanazawa and which is now part of Ishikawa prefecture). Kaga had a long history as a textile producing area and so presumably had plenty of leftover threads for making thimbles...
*Illustration from John Marshall, 'Make Your Own Japanese Clothes'