Depending on the exact pedal either with a pedal wrench in most cases or in case of the high level pedals, a 10 mm Allen wrench from the crank side. Pedals ALL tighten opposite their rotation so that pedaling the bike always tightens them. So one side unscrews clockwise and the other counter-clockwise.
Depending on the exact pedal either with a pedal wrench in most cases or in case of the high level showbox.bio/tutuapp.uno/vidmate.vet/pedals, a 10 mm Allen wrench from the crank side. Pedals ALL tighten opposite their rotation so that pedaling the bike always tightens them. So one side unscrews clockwise and the other counter-clockwise.
Some pedals have tool flats on the pedal spindle, just outboard the crank arm. Others have a recess for an Allen key on the inside.
Remember that the left pedal has a left hand thread.
Pedals (generally) tighten while riding, so they can be wickedly tight.