What do you want to read? Nothing beats actually engaging with something you care about.
More generally you can have a look at the Absolute Beginner Book Club for instance if you’re just dipping your toes.
There’s also Satori Reader that provides graded readers with a lot of explanations. It’s not free but you can sample most (all?) stories before you subscribe.
Keep in mind that, if you’ve only been using WaniKani so far, you’ll probably find that grammar and potentially kana vocab are giving you trouble. If you haven’t studied basic grammar yet, now would be the perfect time. Free resources include Tae Kim and Cure Dolly. Don’t hesitate to jump straight to reading though, and see how you fare. You’ll be able to figure out where you need to focus your studies to improve comprehension.
Regardless of the path you take, reading will be very hard at first. Japanese syntax is very different from ours, as a result you’ll often be frustrated when you encounter a sentence where you know all the words and still can’t figure out what any of it means. At first it’ll feel like every sentence is a riddle you have to solve. This isn’t you being bad, it’s just how it feels to start reading Japanese. It gets better, but it will take some time before it really clicks, even for relatively simple Japanese. Take your time and try to read a little bit every day. Slow and steady wins the race.