Mark the desired spot for the hole on one side of the tree by skinning off the bark with a hatchet.
Measure from the ground up to the location for the hole and the distance from each side of the tree using a tape measure. To account for the curvature of the tree, hold a straight edge against the sides when you measure.
Locate the spot on the other side of the tree using the measurements you took from the first side. Skin off the bark in the location using the hatchet.
Install a long wood bit into the chuck at the end of an electric drill. Hold the drill at a 90-degree angle to the tree on one side of the tree. Hold the trigger end of the drill with your dominant hand and place your other hand under the front of the drill just behind the chuck.
Squeeze the trigger and guide the drill bit into the tree using a generous amount of pressure. Keep the drill straight to drill the hole evenly. Guide the drill into the tree the entire length of the bit. Back out the drill bit while it is still turning.
Drill a hole from the other side of the tree on the skinned area you marked earlier. Use the same procedure to drill the hole as you did on the first side.