Hi dhanley1

Assuming you have AS 3000 V10 (that includes the Custom windows)

To modify a window
Power tools--> window designer--> choose a window--> modify
To select a window and insert in the plan--> Floor tab--> the 8th icon (on the top) is the windows icon--> click on the icon--> the window menu will appear in the preview bar (right of the screen)--> click on the windows icon (top of the bar)--> the last icon is the Custom window icon--> click the icon--> the Custom window will appear--> choose the style (casement, fixed, etc)--> set the dims (don't forget to press Enter after each dimension)

Hope this helps

Patricia