I just installed Marshmallow. I have apk files on my SD card and have in the past used Easy Installer to install them. For some reason it doesn't detect any. I tried another apk installer and it couldn't detect any either. I can use File Explorer to manually navigate to the apk folder on the SD card so I know its there. How can I install apk's (easily using an app) on Marshmallow? I remebered to check option "allow installation of apps from unknown sources".
Go to file manager then explore the directory of sdcard where the apks are exists then click on it to install and check unknown sources if asked by android , by this you know whether the apks exists and supported by your mobile phone new upgrade.
Then you need to go to application manager select Easy Installer and check its permissions required to explore sdcard and install apps. Another important thing is that it may be possible that your apks are old and not supported to marshmallow.
Or you can simply go to application manager then go to Easy Installer clear all app data then restart it. Then definitely it will ask for all the required permissions. or you can check for update , the latest version is 3.1.6 , check it that you have the same else update
another thing is that many peoples reporting at google play that this app is not able to find apks now. here is the url:https://play.google.com/store/apps/details?id=mobi.infolife.installer&hl=en read the review carefully