Assuming you downloaded the correct 64bit version, there is nothing to install.
You download the file, unzip it, and run the EXE. Windows will warn you about the publisher as it always does. you can just ignore all of that.
IF the program won’t run, maybe you are missing the prerequisite development components - you can probably bypass this by installing the stable version with the installer - which will take care of all dependencies, and then just run 2.8 from the zip file afterwards.