Unlike most African countries that are visa free or visa on arrival for Nigerians, you are expected to obtain a visa before scheduling a trip to visit Angola.
You can make your visa applications and enquiries through the Angolan Embassy which is located in Abuja.
The address of the embassy is;
Embassy of The People’s Republic of Angola,
Plot 321, Diplomatic Drive, Central Business Area, Abuja FCT, Nigeria
Email address is firstname.lastname@example.org while phone numbers and fax numbers are +234 9 4614731 and +234 9 4611636 respectively.
The embassy also has a mailing address which is PMB 5145, Wuse Zone 3, Abuja, Nigeria.