• Start create or edit an action.
• Select $User context object (1).
• Select item from context object items picklist (2).

$User context object items:

• Name - concatenation of user's FirstName and LastName. 
• FirstName - the user’s first name.
• LastName - the user’s last name.
• OrganizationId - ID of the organization.
• OrganizationName - the name of the organization.
• ProfileId - ID of the user’s profile.
• Email - the user's email address.
• Id - the user's ID.
• UserName - stores username value used to login to Salesforce Organization.
• RoleId - ID of the user’s role.
• Type - the category of user license.
• TimeZoneSID - user time zone identifier.
• Locale - user locale.
• CurrencyCode - user preferred currency code.
• TimeShift - user time shift.
• DateFormat - user Date format.
• DatetimeFormat - user Date Time format.