Elbow fittings are used to change the direction of the pipe by 90 degrees or other angles. Determine the required angle for the elbow fitting based on the piping layout and space constraints. Ensure that the pipe ends are clean, smooth, and free from any burrs or debris before installing the fitting. Apply a suitable pipe thread sealant or thread tape on the male pipe threads to create a leak-free seal. Hand-tighten the elbow fitting onto the pipe until snug, and then use a pipe wrench to make a final quarter to a half turn to ensure a secure connection. Avoid over-tightening the fitting, as it may damage the threads or cause leakage. Check for any visible leaks after installation and make necessary adjustments if required.