I have a work permit given by dhs.

Well, in that case you should not attempt to register with the Selective Service because you are still NOT eligible. On the other hand, a social security number does not immediately grant you credit. It will only grant you access to begin establishing a credit history of your own. You might have problems obtaining credit until you have been employed for a while and somehow established some record that potential lenders can see and slowly start trusting you as a creditworthy individual. Good Luck!

Thank you for your time, and responses.