Basic qualification is graduation in marketing or if added MBA degree it gives a weight age to your overall profile.
Duties of the Digital Marketing Manager:

• Devising strategies to drive online traffic to the company website.
• Tracking conversion rates and making improvements to the website.
• Developing and managing digital marketing campaigns
• Utilising a range of techniques including paid search, SEO and PPC.
• Overseeing the social media strategy for the company.
• Managing online brand and product campaigns to raise brand awareness.
• Managing the redesign of the company website.
• Improving the usability, design, content and conversion of the company website
• Responsibility for planning and budgetary control of all digital marketing
• Evaluating customer research, market conditions and competitor data.

Now based on your current qualification you can decide your further education and college.