I have the student/teacher version - Even though I have downloaded - or it says it is installed - I can't get the program to open it only takes me back to the install menu.
You must be double-clicking on the wrong icon
You need to find the Lightroom icon, not the installer program icon
It sounds like you are starting the installer again rather than the program. Try going to your applications folder or your program files folder and locate the icon for the Lightroom program in the folder. Double click on that icon to try to start the program. If that works then you should create a desktop icon for the program.