If you wish to regularly use a PCB board outline in new projects, save the PCB design file containing only the board outline. This file can be moved or copied using the Windows file manager into the DesignSpark PCB "Technology" folder as in the following example.
Now, when translating from the schematic to the PCB or creating a new PCB, at the following step in the Wizard "Define you board outline" you can select your board outline.
When you complete the wizard loads your custom board outline will be ready to use.
See also: How can I import a DXF PCB board outline?