How to decode a (Vigenère?) substitution cipher?
This is, in fact, not a Vigenère cipher.

One clue to this is the fact that the ciphertext (which, conveniently, includes unenciphered word breaks) contains lots of repeated words like UTL, VCI, V, UB and QVRY that would be very unlikely to occur by chance in the output of a polyalphabetic cipher like Vigenère.

Another clue can be obtained by examining the letter frequency distribution of the ciphertext: while the letters of the alphabet have obviously been scrambled, sorting the letters by their frequency reveals a very similar distribution as unencrypted English text:

L: 305 #############################################################
V: 248 ##################################################
U: 246 #################################################
B: 175 ###################################
Z: 160 ################################
T: 158 ################################
C: 154 ###############################
A: 142 ############################
O: 140 ############################
H: 131 ##########################
I: 121 ########################
S:  77 ###############
R:  72 ##############
F:  63 #############
P:  63 #############
D:  49 ##########
Y:  42 ########
G:  41 ########
W:  41 ########
K:  39 ########
E:  37 #######
J:  22 ####
Q:  14 ###
X:   4 #
M:   3 #
N:   2


Both of these clues suggest that we're probably dealing with a basic monoalphabetic substitution cipher.

So, how do we break a cipher like this?

One way to get started is to guess that the three most common letters in the ciphertext (L, V and U) most likely correspond to the three most common English letters (E, T and A) in some order.

One of those letters, V, occurs several times in the ciphertext as a single-letter word (in fact, it's the only letter that occurs so).  The most common single-letter word in English is the indefinite article "a", so we might guess that the ciphertext letter V probably corresponds to the plaintext letter A.

Meanwhile, the other two most common letters, L and U, occur together in the most common word in the ciphertext, UTL.  As the most common word in English is the definite article "the", and as we've already guessed that L and U probably correspond to E and T (since V is A), it seems very likely that UTL in fact means "the".

This already gives us the following partial cipher alphabet:

plaintext:   abcdefghijklmnopqrstuvwxyz
ciphertext:  V   L  T           U


We might even go out on a limb, and guess that the very common three-letter ciphertext word VCI, which starts with the known plaintext letter A, might correspond to the common three-letter conjunction "and".  But at this point, it's probably a good idea to just try to decode some of the ciphertext using the partial alphabet we've guessed, just to see if it looks reasonable.  Doing this, we get something like:


  the ZettOnP ZSn RaZt HBnP ZhadBFZ aRABZZ the deRY. theAe FeAe nB FBAdZ, QSZt ZBSndZ. that needHe aHZB Dade a ZHBF ROARSOt aABSnd and aABSnd and aABSnd, ...


(Here, the uppercase letters are still undecrypted, while the lowercase ones have been decrypted according to our partial cipher alphabet.)

At this point, we can just start guessing at the partially decrypted words.  For example, "theAe" is probably "there", so A would be R, and "needHe" might be "needle", making H correspond to L, and so on.

Continuing in this manner (and occasionally checking to see if the resulting partial decryption still makes sense), it should be possible to work out the complete cipher alphabet.  I'll leave completing this task as an exercise, since that's what this is presumably meant to be.  I did verify, though, that it is indeed possible to decrypt the entire message in this manner, and that the guesses I've made above for the decryptions of various ciphertext letters are, in fact, correct.  (Note that this will not always be the case in general; sometimes, you do need to backtrack and try different guesses if it turns out that the decrypted message makes no sense after all.)