If you want to start a digital marketing company, there are a few things you'll need to do. First, you'll need to have a solid understanding of the basics of online marketing. 

Second, you'll need to be able to create effective and engaging content. And finally, you'll need to have a strong email marketing strategy. You can even search online for more information about free online trade courses with certificates.

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To get started, check out these free online courses on digital marketing:

1. ClickZ's Digital Marketing Bootcamp: This course is designed for beginners who want to learn the basics of online marketing. It covers topics such as creating a website, developing an advertising plan, and measuring your progress. 

2. Udemy's Digital Marketing Certification Course: This course is designed for professionals who want to improve their digital marketing skills. It covers topics such as SEO optimization, email marketing, and social media marketing. 

3. Skillshare's Marketing Certificate Course: This course is designed for business owners who want to learn how to market their businesses through digital channels. It covers topics such as content marketing, email marketing, and social media marketing. 

4. Udemy's Job Interview Course: This course is designed for people who wish to prepare for job interviews. It covers topics such as resume writing, LinkedIn marketing, and social media marketing. 

5. Skillshare's Communication Certificate Course: This course is designed for professionals who have a desire to communicate well with others. It covers topics such as body language, time management, and presentation skills.