It depends.
If you are referring to the actual occupation line on the tax return, then you can enter your actual profession. The entry on this line does not affect how your tax return is prepared and calculated.
If you are trying to enter information about your LLC, it will depend. If you have a single-member LLC, then it is considered a disregarded entity for federal tax purposes and would be reported on a Schedule C on your personal return. If there is more than one member, then your tax filing requirement may differ. Please see this link for more details.
You can also see this link for details on entering your business expenses if your LLC is established as a single member LLC.