This is relatively easy. There are lots of approaches to it too. They include social media promotions using Facebook groups, instagram, twitter and Nairaland (If your target market is mostly Nigerians)
But if you have some cash to spare, paid advertising for your product is the way to go. Nairaland and Facebook ads are very affordable.
For me, as a Nigerian seller, I mostly promote my stuffs on Nairaland since they make it possible for thousands of people to see your posts for free but if I want more results then I do banner ads. There are lots of Facebook groups with thousands and millions of users. Write compelling stories that do not violate the rules of these groups but at the same time promoting your product and post these stories in such Facebook groups.
You can also contact admins of these groups to help you promote your products on their groups.
The most effective way to it is however email and SMS marketing. It is by far the cheapest and yet the most effective with high returns on investment. It has been proven several times!