I got introduced to using a thimble at 17 - not desparately young (although perhaps it seems so now) with the instructions
you will learn to use them (one for each hand) but it was when I went to the RSN, and you cannot survive a full working week sewing by hand without some protection, part of it is an attitude of mind, the other part is having the right size/shape (fingers are
not round) sometimes squishing the metal thimbles out of round makes them more comfortable and they sit on the finger better.
I also got fed up going home every night with rust rings around my fingers, until I worked out to paint the insides with nail varnish