Blackmart Alpha is a black market Which can provide you all the playstore apps which are really costly for free !!!
Its really easy to install and nothing complicated !
But for this you must have a rooted phone !
rooting is not harmful if you follow the process carefully for rooting your phone click here
Once you have successfully rooted your phone download the app (the link is given below) just install it and then after opening the app. just click towards search icon and type the name of any app. you want ! it will download your app and then you can either install that app from clicking in the notification bar or either goto MY FILES > BLACKMART>DOWNLOADS there you'll find all of the APK files which you have downloaded through blackmart !
the link for Blackmart : click here