_{This is not a puzzle, this is an actual question}

Recently I tried to solve a puzzle on this site, which I was certain used a Vigenere cipher. I'd never heard of it before the puzzle, so I went straight to the Guide, and later to Wikipedia.

I understand a Vigenere cipher has 3 parts: the plain text, the key and the encrypted text. It is my understanding you would need at least two of these parts; however, the guide seems to suggest you can use the index of coincidence to find the key from the encrypted text, although I may be wrong.

I seem to do okay with Wikipedia's example:

Plaintext: ATTACKATDAWN
Key: LEMON
Ciphertext: LXFOPVEFRNHR

Here Wikipedia explains that the key would simply be repeated to make as many characters as the encrypted text / plain text, so it comes out as LEMONLEMONLE.

From there and using their helpful image (attached as it appears to be in public domain) (click for larger version)

I understand that looking at the L row from the first column (the first letter in the key), and finding the L (first letter of encrypted) in that row, I get A. Using the same logic for the rest:

Row L pos L = A  
Row E pos X = T  
Row M pos F = T  
Row O pos O = A  
Row N pos P = C  
Row L pos V = K  
Row E pos E = A
Row M pos F = T 

and so forth; however, I tried to apply this logic to a puzzle, who's encypted text was cicessrt and key was cantwait, and all I got was gibberish:

Row c pos c = a
Row i pos a = s
Row c pos n = l
Row e pos t = p
Row s pos w = e
Row s pos a = i
Row r pos i = r
Row t pos t = a

The answer is actually meant to be

Star wars

It feels like I tried and double checked everything, including swapping the key + encrypted text (which gives more gibberish) and attempting to start with the plain text and use the key to get the encrypted text (more gibberish), and I'm at a loss. Given the encrypted text and the key, how is it possible to solve the Vigenere cipher? What did I do wrong?