Auto register in UNA from another site

Hi,

I want to make functionality, where when I register in another site for example : Register on the node js after that I want to be auto register on the UNA site. Till now I have found that I will have to use API for this to create auto register functionality using oauth2.

Can any one explain me how do I use oauth2 for both site or any example.

Thanks

Vivek Mishra