If you have a recovery disk that came with your laptop, you should be able to boot from it by hitting F12 when your laptop first boots, and choose it as a boot device, and then from there, install windows.
If you have an iso for a windows installation, then you can burn that to a disk, or a USB, (instructions can be found here http://www.ubuntu.com/download/desktop/create-a-usb-stick-on-ubuntu) and then choose that at boot. I've never installed windows, but I assume you can choose a partition to install it on.
After you install windows, you will likely need to use boot-repair to allow dual-boot (http://sourceforge.net/projects/boot-repair-cd/) and burn this to a usb or CD as well, boot from it preferably legacy boot since it allows you a nice GUI to edit settings, and run boot-repair off the desktop if it doesn't start automatically, use the recommended fix and after that finishes, reboot and allow ubuntu to boot, and there should be a new menu with Ubuntu at the top and your windows installation at the bottom.
Issues: If your screen goes black after running boot-repair, its likely you need to have nomodeset on, which can be done while booting. Hit f6 and navigate to nomodeset and hit enter. Then hit escape and try booting.
EDIT: If you have any questions, issues, or want me to go into further detail on some of the steps, let me know. I might just give you a link where the steps or issues are explained much better than I could explain them