Paid only — there's no free tier. This is the big one: unlike most tools here, you pay before you make a single image. The cheapest way in is the Basic plan (cheaper if billed yearly). First step: go to midjourney.com, sign in with a Google or Discord account, pick Basic, and you're in.
Will you need to pay? Yes — so here's how the plans work. Basic gives you a limited monthly allowance of fast generations, and when it runs out your fast generations stop. Most people who stick with it move to Standard, which adds unlimited "Relax mode" — slower to generate, but you stop counting. One quirk: you're buying GPU time (the computing power to make images), not a fixed number of images, so heavier jobs use up your allowance faster.
If free is a dealbreaker, you're not stuck. Midjourney is the quality benchmark, but it isn't the only option — the catalog has solid free image generators too, a gentler way to test whether AI image-making is for you before you pay for anything. Browse the Image Generation category (linked below) to compare.