The answer to 'how to unclog toilet' is to first try a plunger. Firmly place the plunger over the toilet's drain opening and plunge up and down vigorously to dislodge the clog. If that doesn't work, you can try using a toilet auger or 'snake' to physically break up the blockage. Slowly feed the auger into the drain and crank it to extend the cable and push through the clog.
If the clog persists, you may need to disassemble the toilet to access and clear the drain pipe. This is more involved and you may want to call a professional plumber, especially if you're not comfortable working with plumbing fixtures.