Registration; OAI PMH; DOI

I work in Oporto University, Faculty of Arts and Humanities we have OJS Faculdade de Letras da Universidade do Porto - OJS and I would like to improve the site. I have try to register the site in PKP but I don´t know where. I open a lot of place but most of them send a message of error page not found. It was important for us to do the registration and have the OAI PMH working ok because a lot of databases could harvest ours articles. However even the information of the system says the OAI is active I search the registration in PKP and I can’t find our registration.
Although when you send to so many links that at some point I’ve already lost myself and the information I am looking for.
Other question is about the DOI. We are doing that manually but it was better doing through OJS but I don’t know how that works. We have the prefix that crossref attributed to us and I don’t know where I put that and how I can control the possible problems, because we have a lot of journals and a lot of articles. So can you please help me? Grateful for all the help you can give to me