Replacing stove knobs requires removing the old knobs from the stove by hand and attaching the replacement knobs. Look for the D-shaped part inside the knew knob. Attach the new knob on to the knob's shaft with the D-shape inside the knob facing down.
Most knobs are universal, but it is important to ensure the new knobs fit on the stove prior to purchase. Some knobs are specifically made for gas or electric stoves. If the knobs seems hard to pull off, it may be coated with grease. Use pliers to remove the knobs. After the knobs are removed, clean the knobs' shafts with a household kitchen spray or damp rag before putting the new knobs on.