Oh my...I hope that this is the only problem you have, but I suspect there will be many many more. A reputable and knowledgeable seller would never have sold you a BB with the password still assigned. Anyway, the way to cure this is to keep trying and failing to enter the password...after 10 times (normally, can be fewer), the BB will wipe itself clean and remove the password requirement. Hopefully...
Occam's Razor nearly always applies when troubleshooting technology issues!
If anyone has been helpful to you, please show your appreciation by clicking the button inside of their post. Please click here and read, along with the threads to which it links, for helpful information to guide you as you proceed. I always recommend that you treat your BlackBerry like any other computing device, including using a regular backup schedule...click here for an article with instructions.