Tap Sign up from the Profile tab. The fastest way in is Continue with Google or Continue with Apple (where available on your device) — Kosmos fills in your name and email automatically and just asks for your phone number and country to finish. To sign up with email instead, enter your name, email, phone number, and country, choose a password (at least 8 characters), and accept the Terms and Conditions.
Just want to look around first? You don't need an account at all — Browse, listing pages, your cart, and even checkout all work without signing in. An account is only needed for things tied to your identity across visits: order history, wishlist, messaging, and selling.