Yandex: how to merge sessions?

Question

JavaScript

I read the documentation. https://yandex.ru/dev/conversion/identification/#q... I
registered an oauth application, got a client_id

But I still don't understand how to implement session merging on the site. If I understand correctly, then after authorization on my site, Yandex needs to specify the user id of my site and then, paired with PSUID, there will be a unique identifier that identifies the user. But I didn't find anything in the code.

Tell me, please, who dealt with the question of what should be the algorithm of actions.

Here the person has entered my site. I have his id. How to proceed further to merge sessions?