On page 250 it says

character can often increase his Wounds by spending Experience Points (see Chapter II: Specialities ).

But I look around under specialties and could not find this, am I missing something? The only thing I can remotely find is "Sound Constitution". This lets you get a couple wound points based on the specialty. With some specialties getting none or up to five times.

That is it, Sound Constitution. One point per time it is bought.

I think the average among all specialities available is about 11 to 13 additional wounds.

You can purchase this talent one time for every instance it is present in your advance tables, except when it is followed by a multiplier, then you can purchase it a number of times equal to the multiplier in that instance.

Typically not a worthwhile investment for the cost in DW. Unlike in DH.

A slightly more abstract method I've seen being used is to grant an extra wound per rank attained so as simulating that characters get tougher through their experiences and just ignore sound constitution entirely but this is your own house rules.