If you dont have one, follow these steps.
- Visit your inventory page on browser (eg: http://steamcommunity.com/id/poWar/inventory/)
- On top right of the page, you’ll find a Trade Offers button. On clicking that you’ll be taken to your trade page.
- On the right hand side click on Who can send me Trade Offers?
- You’ll find the trade URL at the bottom of the page