Dude, it’s not easy, but you’ll learn A LOT.
There are two very important aspects, sales and networking. I joined a group called Business Warriors. Nothing too special about the group, but they give a lot of insight into dealing with potential clients. For example, a bad place to be is for a client to see your work as an expense. A good place to be is when they see it as an investment. To you it’s still the same work, but less stress and usually better paid, but that shift in mindsets is up to you when you pitch the sale to them.
The one I’m bad at is networking. There’s no shame in asking for help, just don’t beg. So join as many local business groups as possible on Facebook, and ask if anyone knows someone who can use your skills, or help you with some advice on how to make a success.
You’re not a Graphic Designer. But you’ll be competing against them. (Which makes no sense, but that’s the way it is). Don’t make the critical mistake that I made of trying to compete with them. I wasted 6 months doing that, and it’s hard to explain why your stuff is x10 more expensive than some kid with MS Paint’s work. You have a specialized skill, push that to it’s limits, because there are a lot of people who need that, and will pay good money because so few people can fill their need.
Most of my work comes from people who need stuff for mobile games, or mockups for proposals and things like that. People always have some weird ideas and need someone skilled to show others what they envision, that’s where I come in. (If that makes sense)
Building a website and portfolio.
There’s a big desire to feel all professional and cold and businesslike. Don’t. Along with your skills, people will want to hire you. So throw the things your friends like about you in there (just in moderation, and assuming you have friends who like you )
As for building a professional portfolio, what works well for me is to bid on jobs on CrowdSpring.com
I do try to win, but even if I don’t, I get material that I can use in promoting myself.
I hope this helps a bit. Let me know if you have more questions.