a. On new/second device just go to Android Settings.
b. Scroll down and go to Accounts and backup.
c. On the next window click Manage accounts.
d. Then click "+" sign on next window.
e. Choose Google account from the list.
f. Add the same Google Account (Email address used for app purchase) there.
g. Once added, go to Play Store App and there click Profile Icon.
h. From the drop down list, select the Registered Account.
I. Then search iShala there (in Pay Store Search Box) and it will be available for installation.