From Kalispell, take Hwy 2 toward the West Glacier entrance. Drive Going-To-The-Sun Road up to the Logan Pass Visitor Center. The trail to Hidden Lake (including the overlook) is directly behind the visitor center and it's about 1.5 miles to the overlook.
The weather in the park can be variable, no matter what time of year, so make to pack both warm- and cold-weather clothing for yourself, as well as rain gear for both yourself and your camera. And a tripod is an absolute must, even though it can get so windy sometimes that even a tripod can't keep the camera still.
This photo was taken in mid-August. The weather had been variable, going from cloudy and rainy with 40-degree temps to sunny with puffy clouds, high winds, and 80-degree temps. This shot was taken around 7AM on my very last day in the park. With the exception of one fellow making his way back down from the 1.5-mile path to the overlook, there was nobody else around - the Logan Pass Visitor Center parking lot was totally empty. I had the entire overlook balcony to myself for about 20 minutes. The wind was pretty heavy and the puffy clouds were scudding across the blue sky at a fast pace. This area just begs for the widest wide-angle lens a photographer has in their arsenal.