The Italians only really use 21 letters, but sometimes they do use the other 5 if the word is a non-Italian word containing one of those letters. The 5 letters that are not a part of the Italian alphabet are J, K, W, X, and Y.
A = a
B = bi
C = ci
D = di
E = e
F = effe
G = gi
H = acca
I = i
L = elle
M = emme
N = enne
O = o
P = pi
Q = cu
R = erre
S = esse
T = ti
U = u
V = vu
Z = zeta
J = i lunga
K = cappa
W = doppia vu
X = ics