I did the same thing back in 2009 when I bought a Kent bike shaped mountain object. I rode it about 20-30 times to work before it sat for 6 years. When I eventually started riding it again and it felt small so I sold it off. Then I ended up buying bikes off craigslist to try since I could sell them for about the same price I paid. In the end, I am left with a Sirrus Sport and 29er hardtail for the mountains and I am happy.

Are you still within the return period of the walmart bike? Is it your size? If it fits you, ride it for until you decide what to do. You many not even like cycling and it is better to have a couple hundred dollar bike sitting in the garage than a $1k bike.