I can’t get my desktop keybord to work and I can’t access my perferences because I Need my keyboard to enter my PW

If you can't connect your Magic Keyboard, Magic Mouse, or Magic Trackpad to your Mac

Resolve Wi-Fi and Bluetooth issues caused by wireless interference

Any one of several things could be happening. Have you confirmed that the keyboard's battery is charged? The keyboard should work if you have it connected via the charge cable. Have you recently done or changed anything which may have caused the problem? You can borrow someone's wired keyboard to enter the password and then further check all settings. This is why I never use wireless keyboards.