I was using windows 10, then I installed Linux Elementary OS. During the installation, I deleted my windows. Now my elementary is working fine, just I want to install windows back cause I have work with Microsoft Office and I don't want to remove elementary.
You can download and use gparted software visually and directly vis AppCenter on the Loki. After partitioning HDD as you want, you can install windows on the region of storage partiotioned for windows. There are a lot of partiotion software on Linux but when you are a novice, I recommend gparted software on Loki and more thing is that you can use softwares such as LibreOffice or OpenOffice on many Linux distros instead of MS Office on windows.
I wanted to install windows on my PC after the installation of Loki, but I found out that you cannot partition the SSD/HDD if Loki is currently running on it. I tried with gparted, but it did not work. If it is a fresh install I would suggest that you reinstall it again and try to partition it before the installation.
Hope this helps.
p.s. In the end I installed windows on another HDD, but then the booting time with Loki went to heaven. With windows on the second drive, Loki was booting in like 2 minutes (less than 15 seconds usually). Just keep that in mind.