Creating a disk image, DMG, file is simple.

1) Create a folder and place the contents that you want to distribute into that folder.

2) Run the Disk Utility application. (Found in the Utilities Folder within the Application folder of the hard drive)

3) Click on File --> New --> Disk Image From Folder

4) Select the folder

5) Give the image a name, location and then click Save

6) You are done