For testing purposes, we recommend to use some your sandbox or create new free Salesforce DEV edition. You can use 7 days free trial for the Call Utils as well.
Your Salesforce administrator needn't to know about using Call Utils. It's the same like using the official Salesforce mobile app. You can use the Call Utils for Salesforce if it's not explicitly disabled by your company's security policy. If you have a trouble see troubleshooting or ask your admin.
As an end user, you can find your settings in the Call Utils mobile application, main menu on the main screen (call history). Most settings can be overridden by your Salesforce administrator because it is good for your entire CRM system. If your admin doesn't restrict anything, you can choose to Log a call as a task or event, whether to disable call recording, what action executes after a call, or what language to use for Speech to text.
As an administrator you can set almost everything from enabled API for named users to default values in sObjects created by the Call Utils.