This one?
http://www.bernat.com/pattern.php?PID=259

Here's a site with various joining methods, http://www.crochetnmore.com/joiningsquares.htm

Yes, That is the pattern, but if you go through the pattern there is no diagram showing how to join the squares to make the diagonal looking afghan.
I know how to join squares, I just need to know the placement of them so mine looks like it is supposed to when it's done.

Find some graph paper or print one of these, http://incompetech.com/graphpaper/

It looked like all the squares were the same, right? How many squares did you make? Rotate the graph paper a bit so you have diamonds, not squares, and color that many diamonds in with a pencil. Make a rectangle with jagged sides. Use that for your sewing up pattern.

The following is strictly observation, guesswork, and a little arithmetic. (And it would be really nice if they had shown a picture of the afghan flat, but I couldn't find one, so I had to guess.)

The way the afghan hangs over the chair, it looks like the short edge has six diamonds across, each with a tassel attached. The pattern itself supports this when it says to make 12 tassels, which suggests 6 at each end.

Here's where the arithmetic comes in. The pattern says to make 83 diamonds. From what's visible on the chair, it looks like the end row of six diamonds is followed by a row of five diamonds, then six, then five, and so on, to the final row of six. Pardon the algebra, but 6+5+6+5...+6=83 boils down to 11n+6=83, which gives n=7, and (back to English) seven repetitions of six then five, plus the final row of six. If you draw this on the graph paper as pauline3 recommends (graph paper is good stuff! hard for me to crochet/knit without it), it comes out to eight diamonds along the long edge.

If that's all you need to pull it together, great. The pattern says to sew the squares "in strips", so if you want to do that, back to the graph paper and more arithmetic.

Summary: It comes out to two strips each of one, three, five, seven, and nine squares, plus three rows of eleven squares.

Gory details:

Start with any corner. That first "strip" contains one square. Go in one row diagonally, and that row contains three squares. The third row in contains five squares. The fourth row contains seven squares, the fifth contains nine, and the sixth contains eleven, for a total of 36 squares in this corner section.

If you're looking at the graph, you will see that you now have enough strips to complete the end row. The same pattern applies starting from the opposite corner, so double 36 to account for the opposite corner section, and you have 72 squares, and 83-72=11, so there is one row of 11 squares between the two corner sections.

Hope this helps without being overkill.