Bike, Light, Lock, only change the back tires

One need to change back tires. I was using it for 2 months until back tire blowout last week. I was perfectly fine until this, travelled to Mountain View,Stanford, Sunnyvale, have trips between Sunnyvale and Menlo Park. You need to change the back tires, you can I think do it yourself by buying Walmart. I'll go back to my home country so I don't have time to fix.