Upvote:3
As a Nigerian citizen, you must have a visa sticker in your passport to enter Turkey, unless you have a valid visa or residence permit from a Schengen country, the USA, the UK, or Ireland:
Nigeria: Ordinary, official/service passport holders are required to have visa to enter Turkey. These passport holders with a valid Schengen members or USA, UK, Ireland visa or residence permit may get their single entry e-Visas valid for one month e-Visas via the website www.evisa.gov.tr, provided that they meet certain conditions.
(Source: https://www.konsolosluk.gov.tr/VisaInfo/Index)
If you have such a visa, you can apply for an e-visa at http://www.evisa.gov.tr/.
Otherwise, you should start with the online pre-application for a sticker visa at http://www.visa.gov.tr/.