Have the person create a customer account on your nop commerce website.
Once they have signed up you will need to look up the customer record and see which email they used to signup. Copy the email they used to the clip board because you will need it for the next step.
Go into promotions and then affiliates and Add new affiliate. Make sure to fill in all information and to use the same email you copied in step 2 for the email field.
Click save and wait a few minutes for socialbug to create the affiliate.