To add a PWM enabled output you need to pick a pin that the datasheet shows can be connected to a TC[n].WO[m] pin for some n and m, with the following constraints:
the TC or TCC must not already be used for another PWM output if it is a TC then m cannot be zero if it is a TC then it must not be one of the pair of TCs used for step pulse generationAfter picking the pin, put the appropriate entry in the TC or TCC column of that row of the pin table. See the existing entries for e.g. pin out0 as examples.