To properly use the keystone function, you may need to adjust it to correct any distortion or trapezoidal effect caused by the projector's placement. Typically, this involves accessing the keystone correction menu on the projector or remote control and using the arrow keys to make adjustments until the image is correctly aligned. It's important to consult your projector's manual for specific instructions on how to adjust the keystone and focus functions, as these may vary depending on the model.