Quikr works in the same model as OLX. But I find olx better and more reliable.
The website and app: For both the user interface is pretty easy to use, though not smooth. Also it has loads of ads which makes it annoying to use.
How to use the app to sell:
-take pictures of the product you wish to sell
-upload it on the site
-Buyers will contact you
But the problem begins when spammers are given your contact number.
My Experience:
I had uploaded a pair of shoes that was rarely used by me on quikr. The very next moment I started receiving random calls and sms from numbers that were in no way interested in buying the shoes, but wanted to sell their fridge, 2BHK or car! I was surprised and immediately deleted my number and the ad from their website.
Comparatively OLX has the feature of messaging from the app which protects the seller's identity well.
Last Word: Definitely not a place I would sell anything. Not Recommending!