The answer to 'how to unclog toilet' is to first try plunging the toilet. Use a plunger to create suction and push the clog down the drain. Pump the plunger up and down firmly several times. If that doesn't work, you can try using a toilet auger or snake to physically break up the clog. Feed the auger into the toilet and turn the handle to extend the cable down the drain, then pull it back out. You may need to repeat this a few times to clear the blockage.
If the clog is severe or you can't clear it with a plunger or auger, you may need to disassemble the toilet to access and remove the clog manually. This is a more involved process, so it's best to call a professional plumber if you're not comfortable doing this yourself.