If you're asking this question you've clearly learnt the most important lesson there is to learn in any career... When you know you don't know something look for the people who do!!
I can't tell you the right answer for you, you'll have to find that for yourself, but I can give you a few useful tips from my career which started way back in 2001 :)
The first thing I did after graduating from my Marketing degree was simple - Take the first Marketing job ANYONE was willing to offer me - In my case it was in the "mailroom" of a boutique investment company. Now - You may get lucky and get a head start, but I never regretted the long hours and crappy pay because I learnt the way Marketing worked from the bottom up and I got to see how some REALLY smart people did things. I was only there for a year, long enough to learn the basics of the real world (which bore very little resemblance to all of the fancy stuff I learnt at university) and to learn what the different parts of real marketing looked like.
The next tip is probably the most important driver in my success as a marketer - Marketing is a LOT of things today, and to be successful you need to find the aspect of marketing that you are passionate about. Personally, I'm a geek, I love computers and I love numbers, so digital marketing came very naturally to me, and even while I was trying to steer my career away from it, I just couldn't resist logging in and getting involved in digital conversation. Today it's what I do and I've even managed to build a very successful consulting business in the field... but the secret really came down to it being my passion. Even when I wasn't working, I often found myself spending my free time reading books on digital marketing and consumer behavior BECAUSE I LOVED IT.
Lastly, SAY YES! Then believe in yourself to be able to follow through. It's a little known secret that most people in business never really like to admit, but no one is "born with it" and no one starts their career with 3 years experience in anything. We all start from the same place - Go! If you believe in your ability to do something, and someone asks you whether you can, say YES! confidently and proudly, then figure out how to do it and do it WELL. If you're young and just starting out in your career, a lot of people won't be willing to give you a chance if you don't already have the skills they need... but a lot of people confuse skills and experience... just because you've never done it doesn't mean you can't do it and don't be ashamed to tell someone you can do something AS LONG AS YOU COMMIT TO BEING BLOODY GOOD AT IT. That last part is really important, because if you say you can and don't commit to proving that you could... well... I'm not sure what would happen I've never tried it, but I can only imagine it would end uncomfortably for everyone.
Lastly, a piece of personal advice from someone who's had to hire and fire a lot of marketers over the years... Don't let your masters go to your head, real world experience really does mean a lot and I've seen a lot of younger candidates think they can "skip ahead" because they've got a masters degree, only to fall at the first "real-world" question because they answer in academic gibberish. Don't be afraid to be humble and to start out in a job that you might consider to be fairly "low-level", it's not beneath you, and if it gets you some points on your resume a year from now you'll be stepping up to bat at a higher paying and better job and you'll be armed with all the tools to get the job.
Enjoy this part of your career, it may not pay the big bucks, but you've got an entire universe of different roles to discover and the more of them you can sample the richer you'll be for it!