¿Qué significa “I’m ready for my punishment... Putting that thing with the teeth around my tigh like Silas?”
What’s that supposed to mean? ?

See a translation

okey, let me show you. Silas is a character from the book "The Da Vinci Code" which was also made into a movie, so Blair probably read the book or saw the movie. In the picture I attached, there is a Cilice. As you can see, it is a "tool" to inflict pain to oneself, and you can see that it has small spikes which is what Blair calls "teeth" because they pierce into the flesh just like teeth do when we bite something.
The character, Silas, uses it by putting it around his thigh (I wasn't sure if I could upload that kind of picture so if you want to see more clearly how it works, you can see it in the movie or internet, but it's not pleasent to watch so be careful). So, in other words, what Blair says is that her punishment can be "putting that thing (cilice) with the teeth (the spikes of the cilice) around her thigh" which will cause her pain, therefore the punishment.

Sorry if it was too long. If you're not sure about it yet, you can tell me :)