What is the closest big supermarket to Bei Da Jie or Bell Tower ?

I know, at No. 1, Luomashi Pedestrain Street near the Bell Tower, there a Walmart.
The address is: 碑林区骡马市商业步行街1号.
You can take a bus or even walk to the Kai Yuan Shopping Mall near the Bell Tower and then walk along East Street for about 2 to 3 minutes and then you can see Luomashi. Then you can walk along Luomashi Pedestrain to reach Walmart.
If you are still not clear, I think you can ask your hotel staff to tell you the exact place of the supermarket.

Thanks, I know where Kai Yuan is, I will try and follow your directions tomorrow.