Download it from Google Play.
If you are using taskwarrior and you are trying to use Mirakel from Google Play Store, there is a 99% chance, that Mirakel crashes every time you want to sync Mirakel with taskwarrior server (By the way, easy way to set up server, is at freecinc, which is web based server and just follow the instructions). There is a workaround for that. Go to Mirakel, download the 2.8.1 version and the Mirakel will sync with server without problem.
You should then disable auto update for Mirakel on Google Play Store.