i have an emac whose screen is no longer centered so to speak. how would i adjust or reset my old emac screen. it is kind of bent and not centered anymore

There is not a user-accessible position adjustment as found on TVs and some external monitor.

it is bending/curving

Early eMacs had a problem with a defective video cable (the IVAD cable) that caused image size changes and distortion. I suspect yours has that issue. If so a new cable can fix it, but the one place I'd found that had new, known-good IVAD cables went out of business.

For a test, you can attach an external monitor (requires an adaptor). If the image there is normal, you probably have the cabling problem. Replacing video cables means sticking fingers in areas that carry residual voltages high enough to kill. Definitely not something that is an easy "at home" fix.