Step 1: Download the app from the app store.
Step 2: Sign up.
They will want an email & password - kind of login.
Step 3: give them your phone number
(they won't spam you.)
When you do this, it should stop sending you text messages and just limit communication to the app.
Step 4: what do you want to do from here? click to what applies.
Make all notifications for this app vibration only
Mute all notifications for certain groups