Helenius came on as one of 11 half-time changes and needed only two minutes to add to the goal he notched on his Villa pre-season debut against Rodinghausen earlier in the week.
Lambert's changes came after an opening 45 minutes that could only be described as workmanlike, with chances few and far between at the Rewirpower Stadium.
The best chance fell to the home side, who play in the Second Bundesliga, with Yusuke Tasaka firing over Brad Guzan's bar with a shot on the turn.
The second-half proved a different beast altogether with Villa soon into their stride, taking the lead on 47 when Leandro Bacuna's cross was headed home by the lanky Danish striker.
Bacuna forced a fine save from Bochum keeper Andreas Luthe, and Helenius and Marc Albrighton also missed good chances to make it 2-0.
Bochum had a lucky escape with 15 minutes to go when Bacuna headed a Helenius knockback goalwards, but the ball was cleared off the line by the massed ranks of the Bochum defence.
Luthe pushed a Jordan Bowery shot around the post and Villa were made to pay in the closing stages when Tasaka picked the ball up in the left channel and fired a superb effort past a helpless Jed Steer.