Instructions: Notice that the letters beneath the puzzle are jumbled, but stacked in columns. Each letter must go into a blank square, but it can only go into the column above it. Notice that the letter P in the far left column can only go in one place, because there's only one blank square in the column above it. Same with the letter D in the far right column.
Here's a clue: Notice that the second word in the first line contains only one (1) letter. In English, only two (2) words could possibly go there: A and I. Look in the column below the word. There is no letter A in the column. There is, however, a letter I available. Put the letter I in the blank square. Now, you have a T, R, E, and another I left to use somewhere in that column.