The database provided for you to use in setting up Proactive Customer Support 2020 is named ProactiveDB.  This database is in MSSQL 2017 version so you will need to have that version of later installed.  When you are ready to restore the Database to your database server choose Device and Backup Media Type of File and browse to wherever you unzipped and download the .bak file.  

Screen shot below shows the file located and selected.

Click on the Files Tab and check to see the box is checked for Relocate All Files to Folder.  If this box is not checked the restore may not work and you will see an error message.

If all goes well you should see a message that the restore was successful.

You may want to create a user in MSSQL Server for use in connecting to the web pages.  Remember:  depending on your server (local or hosted) you will need to choose Windows Authentication, SQL Logins, or Mixed Mode.  You will need this userid and password for editing the web.config file.

Next read about the web page installation.