How to include token in API rest

Hello!!  I am trying to create an API rest, I am simply fetching data from a Database via GET.

It works perfectly but, I want to generate tokens so that it has security.

I have searched but still can not find something that can serve me. I was recommended to use https://jwt.io but I really do not understand it, if someone has a document or guide that can send me, I will appreciate it.