This seems to be an assignment/homework. So you should really try to solve it yourself. I'll give you some idea of how you can tackle the problem, but you have to put in your own effort and write some code on your own.
Here are a few ideas on how you can solve the problem.
Classis solution: iterate backwards
You can write a loop that iterates from the end of the string (see the len() function) until the first character in the string (a variable goes from the length of the string until 0). In the loop, print each character after the other.
Slice
String and list
slicing allow you to write a more compact code. So you could just tell Python that you want to slice your string where the slicing starts from the end and goes backwards.
Good luck!
If you get stuck, share your code written so far to get help on that.