Before moving to install, your device have to be configure as follows:
Step 1 : Go to Settings
Step 2 : Scroll down to Security
Step 3 : Select Unknown sources
For devices running an earlier version of Android,
Step 1 : Go to Settings
Step 2 : Open the Applications option
Step 3 : Select Unknown sources, and click OK on the popup alert.
If you installed Telegram,Then you can't install YupApp. Now if you realy want to try YupApp,,then just uninstall Telegram; Don't be upset, All your Messages in the Telegram will be automatically synchronized in YupApp and all the Messages to Your Telegram will be diverted to YupApp. Hence you could have two way of messaging YupApp to Telegram and YupApp to YupApp :) :)