Untrained

Tom is totally untrained.

Source: tatoeba (2273564)

To the untrained eye, these dilapidated buildings and neighborhoods seem to be well past their prime and ready to be torn down, but they’re actually critical links to America's past — national treasures that must be protected, according to the National Trust for Historic Preservation, a privately funded nonprofit that works to save America’s historic places.

Source: tatoeba (8110537)

Giles Headley the younger was a fine tall youth, but clumsy and untrained in the use of his limbs, and he rode a large, powerful brown horse, which brooked no companionship, lashing out with its shaggy hoofs at any of its kind that approached it, more especially at poor, plump, mottled Poppet.

Source: tatoeba (11676172)

Many faults arise through simple jobs being incorrectly done by untrained people; such people must receive and follow precise instructions.

Source: wiktionary