Images should be in dcim/camera/.
Tried ES and it worked but it requires a set up (detailed below) (Root explorer does not need require a set up)
Here is a detailed guide
Do exactly what i do, go into wherever the apk is located, hold the apk, press "more" then "move to".
Touch where it says /storage/sdcard0/download, it will then move you back. keep pushing it until you see 2 images... a sd image saying 0 and a phone saying / ... Touch the / and move onto storage. Hit ok.
Open es settings then app manager and enable install apk automatically.
You should now be able to install the app.