To calculate the median, all you have to do is line them up in ascending order. So from least to greatest. Then you look for the number that's in the middle, that will be your median.
So first line them up in ascending order
11, 18, 23, 32, 33, 41, 41, 54, 56, 58, 67, 70
In this example, the median would be 41 (we have two 41s in the middle but if they weren't the same number, you'd add the two middle numbers together and divide by 2, but since we don't have to do that, your answer would just be 41).
So the answer is 41.