Yes, Student loans DO build credit
Any extension of credit goes onto your credit report and build (or ruins) your credit. Student loans are no exception.
The good thing about student loans is that as long as they are in deferment – they are reported as being paid. This is actually good because it helps building “payment history” even though you aren’t really making payments yet.
You may want to use your new credit card wisely. Make a few purchases, wait for the statement and pay it in full. Avoid carrying balance on your card. It’s very expensive (in interest) and does nothing to build your credit.
A credit score of 661 is not very good, but for someone with your age and status in life – it’s certainly above the average. With time your score will improve.