Firstly, you can create a blog where you can share all your graphic design ideas and past works. It’s an online portfolio of sorts where you can establish your own signature style and present it to people who may be willing to hire or are in need of your kind of services. The likes of designing websites, creating posters, fixing logos or match best fonts and such are jobs that both big and small companies need, and which you can do with your own set of skills and talents. This leads to the second thing you can do to expand your online presence: work.
Working for small companies help you catch the big ones in the long run. The former lets you develop your own style, get your name across, and gets you paid (albeit not as much as huge businesses do). They’re a good start to your career as a graphic designer.