open session from other website

hi for all; i want that users of other website can access to my quiz test opigno as an opigno user. at first i have to insert my users on opigno database (table: users, users_roles) when creating users on my website. but i dont know how to open session on opigno when my user is logging into my website. (i think the code have to be inserted into website's login button) thanks for ideas. Sanachr