Moraine Lake Highline may be ridden as an out-and-back, or as a loop when combined with the Moraine Lake Road. I prefer to ride it as an out and back. The return trip from Moraine Lake is more manageable and the descent down to the trailhead, about 5 km, is super-fast, fun and technical. Worth doing over and over again.
If you prefer to ride from Lake Louise Village, use the Lake Louise Tramline to get to the start of Moraine Lake Highline. Follow the Tramline to the Moraine Lake Road crossing; turn left onto Moraine Lake Road and cycle along the road to the signed trailhead on your right.