First, You will need your Social Booth Key information: 

Email: 
Serial:

If you do not have this information, please shoot us an email to support@photoboothint.com

Please Note: If your license is more than 1 Yr old you will need to pay for the update. The cost is usually $99.  However your software will still work just fine, You just won't be able to receive updates for Social Booth

Second, visit Photo Booth Solutions website here: http://www.photoboothsolutions.com/socialbooth/
Download the trial version, Install and enter in your information to get a Trial Version.
  
Please Note: If you do not want to install the most current version of Social Booth, you can install an older copy here: http://www.photoboothsolutions.com/socialbooth/archive/
You can find the appropriate version by using the date you first got your Photo Booth.  Download that version and simply Run the application.

Here is also a link on how to install software on your computer, this procedure is very simple.
https://support.microsoft.com/en-us/help/4026235/windows-10-how-to-install-programs