If you need to manually raise a car seat, it's usually because the power lift mechanism has failed. To do this, you'll need to find the manual release lever or knob. This is typically located on the side of the seat near the floor. Once you've found it, give it a firm tug to release the seat from its locked position. If your car has a telescoping steering wheel, you may need to lower it first in order to give yourself enough room to raise the seat.
Once the seat is released, you can begin raising it by hand. Start by sliding the seat forward so that you have more room to work with. Then, use both hands to grab hold of the bottom of the seat and lift straight up. The goal is to get the seat high enough so that your headrest is at or just below eye level when you're sitting in it. It's important not to try and rush this process - if you go too fast, you could end up dropping the seat and damaging it (or worse, injuring yourself).
If you have any questions about how to manually raise a car seat, feel free to reach out to a certified mechanic or auto body shop for assistance.