In response to a number of what is essentially the same question, I thought I would post my answer in this thread.
Selling B2B basically follows this process.
1. Build a database of prospective customers.
You want to start with the low hanging fruit, typically targeting companies that already spend money on advertising, because you know they invest in their business and do not try to do everything themselves for free and therefore have a greater likelihood of paying for your service.
2. Contact them.
Depending on your preference you should make initial contact through email, social media or telephone.
This BST provides you with a list of the business that already spend on Google, Facebook and linkedin ads in your chosen demographic and their email, social media and telephone contact details amongst a wealth of other information.