From Hyrule Town, head north to Lon Lon Ranch. You'll need to shrink down at a Minish portal near the ranch house to enter a small hole, which leads to a path that eventually takes you to the base of Mount Crenal. Alternatively, you can use the Ocarina of Wind (if acquired) to warp to the Wind Crest near the mountain.
Once at the base, you'll encounter various rock-dwelling enemies like Tektites. Navigate the winding paths, using your sword and shield to clear the way. There are several areas where you'll need to shrink to access hidden passages or interact with Minish-sized objects. Keep an eye out for Kinstone Fusion opportunities with the Minish living on the mountain, as these can unlock useful rewards. The climb itself is a puzzle, requiring you to find the correct sequence of shrinking and growing to progress.