Macbook Air 2012 memory upgrade
Congratulations, that is a nice price! Unfortunately the RAM is soldered to the logic board. So changing simple RAM DIMM's is not possible. The only way to upgrade your RAM is to swap the old logic board with a 8GB memory logic board. In most larger (official) Apple Stores there is the knowhow on how to swap logic boards. But I do not know the costs and I think it is not an economy wise decision.