If Windows is preventing you from installing Respondus Lockdown Browser, You just need to click "Change My App Recommendation Settings" and adjust the setting to stop Windows from showing this notification. Videos showing how to bypass this message are here:
NOTE: If your computer is in S Mode - you may not see all the options listed in the videos. If you're in S Mode, you need to complete the steps in this video: https://www.youtube.com/watch?v=aeU0Y0vk57k