I'm skeptical Walmart is selling fins appropriate for diving, probably more for snorkeling. You might get by with them, but when you're diving you are pushing not just yourself but all the equipment, and you're more likely to run into water conditions that call for better fins.
You don't have to buy expensive fins. You should be able to get decent enough new fins online or even in some dive shops that aren't all that expensive, or a good deal on used ones if you keep looking around. Remember to try the fins on over whatever booties you get, or at least ones with similar thickness and sole.
If Walmart has Deepsea booties they're probably fine to use, just try them on for fit. You don't want them flopping around but you don't want them strangling your feet either. The right size should be obvious when you try them on, look for a gentle hug.
Take your fins (and any other gear you do get) with you for any diving you do later. Even if rental gear is included where you go to dive it is often not so great, and you will appreciate having decent fins that you know fit.