In the New <type of project> Project dialog box, click Customize. The Custom Project Size dialog box appears.
Customize the size of an Adobe Captivate project
When you start creating a new project, you are prompted to choose a predefine size for the project. You can also specify a custom Width and Height for your project.
If you want to reuse the custom size frequently, you can save the project size and assign a name to it. By doing so, you get to choose the custom size from the Select menu the next time you create a project.
Click New and type a name for the custom size. For example, “Size for Adobe Projects.”
Specify the height and width.
Click Save and then click OK.
The saved custom size now appears in the Select list of the New <type of project> Project dialog box.