If another user has your username they can send you a trade. Please refer to our 'sending a trade' article to see how this is possible.
Trading is an important way to complete your collections. You and other users can use trading to swap unwanted duplicates for desirable cards.
If you have push notifications enabled in your settings, you will receive a notification when someone sends you a trade. You can click it to take you directly to the trade screen.
If not, you can see your incoming trades by clicking the back and forth arrows to the right of the bottom menu bar in the app.
You can click each trade to see what is being traded in and out. If you're not happy with anything in the trade, you can turn it into a counter trade or, refuse the trade completely by clicking 'cancel trade'.
If you are willing to make the trade, click 'accept trade'.