Few things to note down are:-

1. Calling import inside a function in Python is however generally not recommended as importing modules is a relatively expensive operation.

2. What you are trying to do is passing argument to the file MyFunction.py which needs to be handled by the code itself as system arguments .Hence to call a function from a Python file from the terminal, you’ll need to modify your file to accept command-line arguments or to define a main function that calls your desired function.

   if __name__ == "__main__":
       input_list = list(map(int, sys.argv[1].strip('[]').split(',')))
       a = np.array(input_list)
       MultiplicateLists(a)
   

Now You can easily call it by the following command:-

python Myfunction.py 1,3,5,6,4,6,7,1,2,7

You cannot execute a Python program in that way. You need a main driver part which reads the inputs, creates an array, and passes them in to the MultiplicateLists function.
So add the following to the end of your file:

if __name__ == "__main__":
    numbers = []
    for x in map(int, sys.argv[1].split(',')):
        numbers.append(x)

    print(numbers)
    MultiplicateLists(np.array(numbers))

You can now run the script by a command in the following form:

python Myfunction.py 1,3,5,6,4,6,7,1,2,7

Just for future readers, I write here down the code that worked for me.
This code employes the solutions of @Prateekshit Jaiswal and @OldBoy, who I thank a lot!

def MultiplicateLists(a):
    import random
    rand_list=[]
    for i in range(10):
        rand_list.append(random.randint(3,9))
    b = np.array(rand_list)
    result = a * b
    print(a)
    print(b)
    print(result)
    
if __name__ == "__main__":
    import sys
    import numpy as np
    input_list = list(map(int, sys.argv[1].strip('[]').split(',')))
    a = np.array(input_list)
    MultiplicateLists(a)

Then, in the terminal, I type the following:

% python3 MyFunction.py 1,3,5,6,4,6,7,1,2,7

And I get this result:

[1 3 5 6 4 6 7 1 2 7]
[7 4 6 9 6 4 5 7 7 6]
[ 7 12 30 54 24 24 35  7 14 42]