You can download the OrCAD software from the below given link.
Installing this software is a bit complicated. When installing this be very careful to choose the necessary features only. The most important facility is Layout Plus. There are so many features. You will have to get a very good understanding to design a PCB (Printed Circuit Board) with this.
The first step is to open a new file and remember to save it regularly during the project. Then go to Library Manager to create the necessary components for your projects. There are many components added in the library itself such as Switches, IC, LED etc. But for a beginner it is important to get to know the software very well. I recommend by creating your own library.