You pick a country when you sign up — it decides which listings show up in Browse, since Kosmos only shows you items from sellers in your own country. You can change it any time from Profile > Account settings, right below your phone number, from a full list of countries with their flags. Switching countries changes what you see in Browse going forward; it doesn't move or hide any listings you've already posted, or affect orders you've already placed.
Help › Getting Started