The screenshot shows none of the css and likely js not working either. Is this being installed locally or on a subdomain? Any info on your hosting spec. The installer part is Codeigniter 3 with mod_rewrite plugin required (which can cause this break of files from before).
It won't let me download the file it just opens a blank page. Below is what the stylesheet/js links look like. I am guessing those are wrong because it is including the /index.php?. When I edit that partout in the inspector it loads the css. The source code also lists the site route as http://build.test.net/index.php? which is where those links come from.