If you tap on your profile from the home page or any page (recent results) you'll be able to see an edit icon next to your username. You'll need at least 1000 points to change it though.

I have over 1000 points but I don’t see the edit button?

yeah, i've made the custom usernames a PRO feature. let me know what username you want and I'll manually change it for you

Can it be FantasticSiurek?

depends. are you from poland?

Guess it doesn’t matter, thanks a bunch for updating, now I can recognize myself on the lists. Cheers