If you DO NOT have a BPL eCard or a physical BPL card, then sign up for a BPL eCard. Check your email for the eCard number–and remember your PIN. Then follow the directions below.
If you have a BPL eCard or a physical BPL card, then:
Go to BPL's A-Z Online Resources, then click JSTOR (or any other database you want to access).
Enter your BPL eCard number and PIN. (Or, if you have a physical BPL card, use that account info.)