You can enter the dimensions of the graph by accessing the WINDOW menu. To show this menu you enter . You will see the window shown in the figure below.
The Xmin and Xmax values are the left and right endpoints (respectively) for the x-axis. The Ymin and Ymax are the lower and upper endpoints (respectively) for the y-axis. The Xscl and Yscl are used to enter the increments for the tick marks. In the example above, there will be a tick mark at each unit. Since it is not necessary to have any tick marks, you can set these values to 0. In fact, if you have too many tick marks you will get an "ugly graph".
If you get an error message like the one below, you have not made the Xmin less than the Xmax or the Ymin less than the Ymax.
To change the values in the window, just scroll down using the cursor and enter the values that you want.
Unless you have a good idea of the window you want, using this method to find a good window can be time consuming and frustrating. There are several more efficient ways to find a window that are discussed in the next sections.