Caesar 's box technique is used here to encode the string of letters.
To decode first the length of the string is to be counted then it's square root is taken and then its rounded of to the closest whole number.
This number is used to cut the string into shorter strings of the numbers length and is placed one below the other. Then the message may be read by the columns so created from top to bottom.
A O O L I W M U V T E E S E S Y O D
Has 18 characters. Sqrt (18) = 4.26 => 4
Now 18 - 16 = 2. Which means 1 additional character has to be selected for the first 2 rows
A O O L I
W M U V T
E E S E
S Y O D
Now reading top to bottom column wise and doing that from left to right the message reveals to be
AWESOME YOU SOLVED IT
Similarly the next line is CRACKED THE CODE RIGHT.