What are the best practices for submitting an application at one of the large global branding firms?

I would like to apply for a position at a large branding firm. Problem is, I have always worked for myself as a consultant and owner of my own agency for many years. I do have a large portfolio of across all verbal practices: naming, voice, messaging and content strategy, and content creation
. I have also done most of my own design, created countless presentations, and developed my own branding methodology, which results in a brand driver report. I speak Korean, and have two masters degrees, one in art history, one in Asian religions, all of which help energize my work. However, I do need help framing my portfolio, simply because I've never worked in an agency as an employee. If you feel confident that you could help me strategize about this job search…