Click on your username on the top right and then click on 'Xper'. Under that section, there will be a button for redeeming your points on the right. If you're on mobile, someone else will have to assist you as I have no idea.
Under your profile, go to the "Xper" tab. From there, there will a button that says "Redeem Points." Choose that and then type a message to the admins about what which prize you would like. They should get back to you within 24-48 hours and it might take a bit longer for the item to get to you.
In the dropdown box, just click "Redeem Xper" and then in the details box, explain what you want to redeem your points for. If you are getting an Amazon gift card, let us know what Amazon store you would like to use (we offer cards for the UK, US, CA, FR, and DE stores) and if you are requesting to feature a question, please provide the URL address of the question you want to feature. :)
Hover your mouse to your account name on the top right of the page, click on the xper option and then click on redeem points.