I am stuck on the puzzle where you have to move all the tiles to make a..

I have just used this method and I has worked I am so relieved it was driving me mad! Good luck.
The Method
Now that you know what a sliding tile puzzle, why not try one? If you don’t have one on hand, there are plenty all over the internet for you to play with. If you’re using a picture puzzle, it may help to have a copy of the completed image on hand that you can draw lines through, so you know the content of each square.

For this guide, I’ll assure a numerical puzzle is being used. To begin, move the number one into it's place in the top left of the puzzle. Continue along the horizontal top row, putting into place all pieces except the one on the right. You should be able to do this without any trouble, and without disrupting other pieces you have already placed. When you come to the last piece of the row, it becomes slightly trickier, and this is where most people tend to get stuck. Begin by placing this piece on the square below where you want it to end up, and make sure the empty space is directly below it. Now, follow this order. This is the most important thing you can learn, so memorise it if possible.

Down, down, right, up, left, up, right, down, down, left, up.

If you followed this order, the entire first row should be done! Don’t worry if you disrupt other pieces along the way, this is perfectly normal.

You should continue to follow the above steps until you have only two rows left. At this point, you will need to turn your puzzle 90 degrees to the right, so the number 1 is in the top right corner. Now you have two vertical rows left to solve. To start with, move the new top left (old bottom left) piece into place. After this, we have to put into place the tile to the right of it (the one that used to be above it). For this, we’ll use the method we originally used to place the tiles at the end of each row. Again, remember that the tile you need to place should be below where it needs to be, with your empty square below it.

Continue this until you’re down to just a 2×2 square. This is the easy part! Simply keep rotating the pieces until they pop into place. Congratulations! If you followed this method, you’ve just completed a sliding puzzle in what I believe to be the quickest way possible. Now, if you’ve memorised the method, amaze your friends and family with your new found talent.