The initial step is to log onto the AppExchange [https://appexchange.salesforce.com/ ] and search for TwixRiva
Once in the listing [https://appexchange.salesforce.com/appxListingDetail?listingId=a0N3u00000MBq5bEAD ] , select Get It Now .
Follow the steps requested by the App Exchange.
You can select ‘Install for Admins Only’ to start with. You will be able to assign Permissions to other others later on in the setup.
When completed, please go to the App Installation Guide page.