Cutting the bottom of the bamboo by about an inch should encourage new root growth, especially if the plant is still healthy. Bamboo is quite resilient, and as long as it's in a water container with enough light and nutrients, it should grow new roots fairly easily.

As for dipping the bottom in wax, that's not necessary. The wax is typically used in some plant propagation methods (like with some succulents) to seal the cut and prevent water from entering, which can help in reducing rot in certain cases. Bamboo generally does well in water, and as long as you change the water regularly (every few days).

Just make sure the cut end is submerged in clean water, and that the leaves are getting some indirect sunlight.

A word of caution, bamboo planted outside can become quite invasive and very quick to grow beyond an intended planting area. It can be destructive to the natural environment and suppress native plant species. In fact some communities prohibit its planting, or example Worthington OH https://www.worthington.org/634/Bamboo-Legislation