Hey there! It's not often we get readers here on the forums, it's usually just creators! Welcome! 
So basically how it works is you pay money to buy ink, not via subscription but you just buy a set amount, and then you spend ink to unlock chapters of premium comics and novels. I'm pretty sure you need to unlock as you go, not in bulk, but you do save ink/money by turning on "1-tap unlock" so that's worth doing. If you run out of ink, you'll need to top up your wallet by buying more. When you buy ink in larger quantities, you make a saving by buying in bulk.
You can also earn ink via the special offers; watching adverts, doing surveys or playing sponsored games can all get you free ink, but they do take time. Also be sure to check in the app every Monday to get your fortune cookie, which is usually around 300-400 free ink.
You can also spend ink to support creators like a tip! Even those of us who make free to read comics. We're always happy for it!
If you run out of ink and are waiting to accumulate more, you could always check out the free to read comics and novels on the site. You can filter to "free to read" using the tags when you're browsing comics of novels (on desktop it's on the top right, and on mobile it's at the bottom). There's some great free content on the platform.