You have to go out and get clients.
Before I made a website or got business cards or anything structural for a business, I simply went out and got a few clients. I decided on my pricing (which turned out to be too low and I raised it after the first couple said yes) and I made free ads on Craigslist and Reddit. I sent messages to my LinkedIn contacts and direct messaged owners, founders, and CEOs on Instagram. I got 4 clients in less than a week.
My first 4 clients were writing articles, doing a press release, website copy, and a blog.
As soon as I saw people were willing to pay me, I put more effort into finding more clients and grew from there.
All I had for my first few clients were a couple of writing samples pulled directly from my personal blog. I still only use my blog as evidence of my writing style, as most of the work for clients is ghosted anyway.