Digital Marketing Agencies will understand what their strength is, what problem area they address, and where you will find these people with such problems.
They can use these tools to reach out to their customers.
- Linkedin
- Quora
- Snapchat
- Online advertising
- Network
- Blogging
Still, it all depends on what they want to sell and to whom.
I would recommend this Digital Marketing Training Course if you want to learn Digital Marketing.