From what I understand you are wanting to implement a code that is able to assemble a list with 5 values, check the highest value element and then specify the index of this value.
Well, when you do:
for c in range(0, 5):
num.append(int(input('Digite 5 valores: ')))
The code captures the entered value and tries to insert into an object in a. This object, which should be defined earlier and which is of type list. Only you have not defined it previously. So such object - list - cannot be fed.
Another thing, Python already provides a function to calculate the maximum value of a list. In this case the function is max().
Also, for you to relate index with value you can use the function enumerate.
By paying attention to these observations you can implement the following code:
num = list()
for i in range(1, 6):
num.append(int(input(f'Digite o {i}º valor: ')))
maior = max(num)
for indice, item in enumerate(num):
if item == maior:
print(f'O maior valor é {item} e possui índice {indice}')
break
Note that the first for assemble a list of the 5 values passed. The second for will go through the list in a and will check the item whose index has higher value. And, if this item has the higher value it will display the respective item and index.
Also note that this code has a break. This will serve to interrupt the execution of the second for when he finds the maximum value item.
Now, if the list has more than one item of higher value, you can remove the break.
This way the code will be
num = list()
for i in range(1, 6):
num.append(int(input(f'Digite o {i}º valor: ')))
maior = max(num)
for indice, item in enumerate(num):
if item == maior:
print(f'O maior valor é {item} e possui índice {indice}')
In the latter code we can list all the values of the list that may have greater value.
Now, if you want to capture all values from a single input(). You can implement the following code:
num = list(map(int, input('Digite os 5 valores: ').split()))
maior = max(num)
for indice, item in enumerate(num):
if item == maior:
print(f'O maior valor é {item} e possui índice {indice}')
Note that when we execute this code we receive the following message: Digite os 5 valores:
. At this point we must type all the 5 values, in the same line, separated for a single space and press Enter.
From this moment the entered values will be mounted in the name list in a. Subsequently the highest value (max()) will be calculated and then the result is displayed.