The easiest way is to move the "OnGrid" folder to the other computer. If you also want to make a Desktop shortcut on Windows, right-click on "OnGrid Tool.xls" then choose "Send to" then "Desktop (create shortcut)". When opening the Tool, it may suggest using the "Master File" in that folder. Please go ahead and confirm using that Master File.
You can also do a fresh install, except that you needn't set your username and password again if it's already set. Fresh installs are particularly recommended for users moving from Windows to Mac. To restore customer data and Tool settings after a fresh install, follow the same steps for sharing info with a colleague, except that you're transferring info to your own computer and not a colleague's.