Hello and welcome to iMore ... The app is located in the Apple App Store on your device. Here is a direct link that will allow you to download the software to iTunes, after you download you can sync your iPad to your computer.
[URL="https://itunes.apple.com/us/app/wechat/id414478124?mt=8&at=10l3Vy]https://itunes.apple.com/us/app/wechat/id414478124?mt=8[/URL]