Couple of things I can think of to consider. The closer/lower down toward the center of the screen you can put it, the better, but not optimal for most people. There needs to be a little room on the backside of the projector for the cables and airflow, keeping in mind the cable cover will add a couple inches on the rear. Try to make sure it's placed "dead center" to the screen, using string or tape measure, from the upper corners of the screen to the lens.
Level it, and adjust to center, rotating the mount left/right/up/down. There is a "click" on the horz lens shift knob, that you can feel, indicating where center is on the shift control dial.
The image should be square on the screen or wall, but maybe a little high which will be adjusted down with the vertical shift. If the image isn't square, check the level and l/r axis. Try to not use the keystone feature if at all possible. Once it's square and center, use the vertical shift up/down and the zoom to fine tune the image onto the screen. Then set the focus.
There are built in patterns that can be pulled up on the remote, or menu, to help aligning it onto the screen and adjusting the focus. It's pretty nice picture right out of the box not needing much change of settings. Maybe that helps some.