You've actually asked two different questions
What should I even write for it to boot into the actual OS, so I can access the files and things?
The fact that you have a prompt
[root@localhost ~]# means that the "actual OS," Linux has successfully booted and you have admin permissions (root). I think you want to start up the GUI. Try entering
init 5 If you have a window manager and desktop installed, this should reboot the system into GUI mode.
I would like to enter boot manager and set boot option to CD, so I can
install Windows 7, how do I do that?
This answer is not exactly the most technical, but it has always worked for me. Reboot your machine and watch the screen closely. Look for something like "Press ESC (F12, F2, etc.) to enter BIOS setup utility." and do THAT. Once in the BIOS utility, you should be able to find an option like "Set boot order" where you can move CD/DVD to the top of the list. Make sure to save settings before you reboot.
Some system BIOS utilities have the option to set fastboot. If that has been set, you may not see the message telling you which key to press for the BIOS utility. In this case, you have to guess. Reboot the machine, and while still in the black screen, just mash a bunch of keys. The most likely candidates are ESC, DEL, backspace, or the function keys (F1-F12). If it doesn't work, keep rebooting the machine and try again.
Best of luck.