The App for your MyTag Bluetooth Trackers is called "MyTag Finder". 

Sometimes a different "MyTag" app appears on the App Store from an Indian company using the same name (breaching our trademark!)   

Make sure you search for "MyTag Finder" as the name.  The App Icon should look like this: 

If you are still unable to find the App, use the following QR codes with your phone camera: 

If you are on your phone reading this you can use the following links to get to the correct App

iOS (Apple App Store) : https://mytag.pro/MTFiOS

Android (Google Play Store): https://mytag.pro/MTFand