Not able to use DAI's permit() function

I’m having trouble testing the permit() functionality from the DAI contract. I’ve read the documentation and a couple of other resources, although, I got the contract code and deployed myself a copy of it on a local machine testnet and got no success trying to make use of it. I’m very confident I’m not using the signature right. What v,r,s values am I supposed to provide to my function? Because, to my understanding, I need already a Tx or a Message+Signature to get my v,r,s values. The lack of resources or practical examples is difficulting my progress because I’m not being able to figure out how exactly I should do it. Thus, I would really appreciate some help here.