I want to ask a question, how to change permission to the element by Sharepoint Online ? How could I identify user. Could I Identify user by email ? Or it should be done only by account ?
Since the OOB powershell commands for SharePoint online don't include changing permissions, this is something that will have to be done via CSOM. You can code it yourself, see here for an example, or you can use the SharePoint PnP project, and use the code that others have already written and tested. This page lists all the available PowerShell commands that are in the PnP project. Just do a find on the page for the word "permission" to find the applicable cmdlets. This page has the installation instructions for getting started with it.