Here is the script copied from the link.
Set-UserPhoto "username" -PictureData ([System.IO.File]::ReadAllBytes("C:\Users\Administrator\Desktop\photo.jpg"))
This part is the pathname: C:\Users\Administrator\Desktop\
This part is the filename: photo.jpg
Where (meaning the pathname) on your system is the desired photo?
What is the photo's filename?
Create a backup copy of the photograph file as a precaution.
Once you have established the full path to the photograph with respect to your systems then you can edit the script accordingly. May not require much change.
Open Powershell in your normal account. You should be able to copy and paste in the script provided via Method 2.
Then edit the path and file name as necessary.
Hopefully the script will run and the method work. However, you may be notified that admin rights are necessary to run the script.
If so just copy the script, exit Powershell, and reopen as an administrator. Paste in the script and try again.
Pay close attention to any errors or syntax information that may appear.
Take your time. Feel free to google "Get-UserPhoto" more information and details.
Here is an example link:
https/technet.microsoft.com/en-us/library/jj218694(v=exchg.160).aspx
The provided examples will be helpful.