CalGraph usually begins with the values of x running from -5 to 5. This may be what you want, but probably it isn't. To change the Domain, click Customize and then Curve Domains/Range.
Enter the lowest x-value you want in Xmin and the highest x-value you want in Xmax. Click Apply and CalGraph will redraw the graph with your new domain for x. If you like the result, click OK or Close.
More likely you will want to change the y-values as well. Enter the lowest y-value you want in Ymin and the highest y-value you want in Ymax. Click Apply to see the difference. I often need several tries to get the Range the way I like it. Once you are satisfied click OK or Close.
There is a shortcut to this window: Ctrl+m
If you have several different graphs, you can have a different domain for each one.