I also like Remind because it creates a safe environment for me to send text message alerts directly to my students (and the parents who also can register to receive them). I call Remind "safe" because my texts are not sent from my phone, I can never see the personal cell phone number of anyone receiving my texts, and all messages are permanently stored on Remind's server.
The Remind support materials are terrific. Here's the link to its Help Center, which has articles on topics like product updates, a getting started guide, and information about making changes to your account.
Remind also has its own channel on YouTube. There you can find 22 excellent short video tutorials on how to use Remind. This video (1:02) discusses how Remind works.