Are you connecting your wifi to your Afrihost line?
Although it's usually all in one device these days, you need to connect the modem part of your device to the Afrihost network; your wifi router part of your device then lets you connect to it.
The modem settings can be found at the link below (you should also have recieved an email when you signed up with Afrihost):
Once you have these settings, you'll need to look at the manual for your wifi device (try Google if you don't have it) for instructions on creating a new connection, because every device is slightly different so the menus and buttons will be different.
If you're just trying to connect your phone or tablet or laptop to an existing wifi, it's best to look at the manual that came with it - newer devices can use WPS, which is as simple as pushing a button on your router, but older devices require more (easy) steps.
Hope that helps - good luck! :)