First step - check the docs
but to answer your question, use the page parameter
http://api.stackoverflow.com/1.0/users/113124/favorites?page=2
ok, http://api.stackoverflow.com/1.0/help/method?method=users/{id}/favorites for the route in question users/{id}/favorites
each item listed under parameters can be sent as a query string parameter.
e.g.
http://api.stackoverflow.com/1.0/users/113124/favorites?page=2&pagesize=100
all of the information is there, explained in detail. The only thing missing is an example url to bridge the gap. I think that would go a long way towards making the docs more intuitive.
But in any case - there you go.. good luck.
