Hello, please help a brother

The purpose of my visit to Moziambique is for a 1 week seminar, I already got the Invitation letter and the flight ticket which was sent by the Organization, but all search on Moziambique embassy in Nigeria and other document I need to take along proves abortive,
Here are my questions:
1.Am sure I need a visa, How do I apply for one or is it upon arrival?
2.what document do I need to tender at Port of entry?

Sidenote: The travel itinerary is from Lagos to South African, South Africa to Moziambique

Thanks for your response.