how to view the sms message send to ringcentral account phonenumber

Login your sandbox or production web service. Check which extension is assigned with this company main number (normally it is assigned to the operator). Login your softphone with that extension credentials then you will be able to receive and view SMS messages for that number.

You can install softphone application in your mobile or install RingCentral phone app in your desktop to get all your messages, fax, attachment etc