Navigate to  Administration -> Enspire settings 

Search for Employee Code Generation setting, below options you can see in the drop-down

Manual: While creating employee you must enter the employee code manually

System/Automatic: Based on employee code auto generation configurations system will ask you to select certain data like company/location/branch/department/date of joining, accordingly system will generates employee code automatically and you cannot override or update it manually 

Both: Both manual and automatic employee code generation are possible

Below is the popup in Employee Master screen when you select as System/Automatic or Both option in Enspire Settings. You have to select Company, Location, Branch, Department, Employment Type and Joined date based on that system will generate employee code.