To use it, download the app from the appropriate app store. Launch the app and search for "Miami." Tap on "University of Miami." Tap on the "LOGIN WITH CANE ID" button. Enter your username and password and you should be good to go. If you are using "special Blackboard credentials" (non-Cane ID) you will need to tap that link TWICE to get in. (Not sure why.)
The Mobile Learn app costs $1.99 for a year of use, or $5.99 for life. There was a free version in the past. It is no longer available. UM is considering purchasing a site license for the app, but has not done so at this time.
Note that the app gives you access to some of your course site material, but not necessarily everything. Be sure to use a web browser to access the site regularly to see if you are missing anything with Mobile Learn.
UM also has Blackboard's Mobile Central application. Mobile Central provides access to general UM information. It is called UMiami on the various app stores.