Creating a gusset in a bag

I am currently making a bag and i found it quite an easy task until i got to the point where i had to insert a gusset. I was really not quite sure what a gusset was as i had never completed one before so i looked it up in my books and on google but couldn't really come up with anything that would help me complete the task. Next i went to the forums in which case somewher there pointed out a link to me of how to go about completing one. For everyone who may need some help completing this here it is.

http://craftydaisies.com/2007/08/24/how-to-square-bags/

Here is how i completed the task.

Here is my basic outside of the bag where i have sewn both the main panels together all around the bag.

Next align the right side seam with the bottom side seam forming a triangle as shown above.

Once you have done this you can chop a little off in order for the bag to sit flat.

Here is the final product showing the square corners on the bag, there are seams coming out from the corners that look a little like darts, however they are hard to see from the photo, you need to be close up in order to see them.