In general, you need to download the “.apk” file from a project, and run it using your android device.
For most devices however, it won’t allow you to install apps from outside the default app store, unless you set the appropriate settings. This is usually done if you go to “Settings” -> “Security” -> “Unknown Sources”. If you tick that, it should allow you to install “.apk” files from the web.
Keep in mind though, that setting is disabled by default on purpose. It’s possible to download and install malicious apps randomly from the web, so check twice before installing something.