I am a new user of nexus 4. I downloaded some apk file from my pc and transfer it to download folder of nexus 4. But the problem is that, apk file not visible in my phone download and i can't install it. so please help me.....
You can download it directly here: Total Commander - Android
As a general warning, though, don't make a habit of downloading and installing apks from random sites, because (a) you have a higher chance of installing malware, and (b) some of those apk files may be for apps that are supposed to be for purchase (i.e., pirated). Whenever possible, you should install apps from legitimate sites like Google Play, Amazon Appstore, GetJar, etc.
Pretty sure you just need a file explorer on your phone like es file explorer and in settings check the unknown sources box to allow the installation.