What do I need to do if I have a girlfriend from the Phillipines and she has a son from a previous relationship to bring to the US?

You can sponsor your girlfriend for her fiance visa and sponsor your future stepson (depending on his age) for a derivative visa, and they can both process at the US Consulate in Manilla. There is a requirement that you must meet in person no more than 2 years prior to the application date. If you are not currently working then you can enlist a joint financial sponsor to file the I-864 form. You should retain counsel to handle the case from start to finish so that the case will be processed successfully and without delays.