You can start by taking the gondola from Skyline Queenstown (fee required). From the top station, follow the clearly marked signs toward the Ben Lomond Summit. The trail is mostly open and easy to navigate. The incline is gradual up to the Ben Lomond Saddle, but the final section to the summit is the most challenging, steep, rocky, and fully exposed above the tree line. There is no shade, and it can be windy and cold even in summer, so bring enough water, sunscreen, and warm layers.
The return distance from the gondola is approximately 11.1 km with around 1,000 m of elevation gain. The final climb is tough but absolutely worth it; the 360° views over Queenstown, Lake Wakatipu, and surrounding peaks are unforgettable. You might even spot a curious kea at the summit (please do not feed them).
For a more challenging full-day hike, skip the gondola and start from the base via the Tiki Trail. This option is approximately 15.5 km return with about 1,443 m elevation gain. The first section up the Tiki Trail is steep and demanding; the track then continues toward the Saddle before the final steep push to the summit.