how to create a new administrator access from a recently bought used macbook?

Do you have the install discs that came with the used MB?

Is there data on there you want to keep or do you want to start fresh?

These constraints may impact the best way to go.

Get an appropriate installer DVD such as Snow Leopard, if it doesn't require Lion or later, boot from the installer disc, run Disk Utility from the Utilities menu in the menubar, then erase the drive and install OS X.

Kappy's right - unless there's stuff you need to save, in which case - back up 1st to a bootable clone; then do what Kappy suggests, then migrate back from the clone what you need to save .... It's a bit more specific than this but I'd hate to see you lose stuff you want to keep ....

Remember that any App Store purchases by the previous owner cannot be used, so nothing is likely lost that you need to keep. Better to have a fresh start because you don't know what was installed by the previous owner. The previous owner cannot sell you licensed software unless they provide the installation media and license codes. Because those would be separate erasing them doesn't mean they are lost.

The computer came from Amazon, but not necessarily FROM Amazon as refurbished. The safest route is to erase it completely and start from scratch.

I agree with Kappy 100% (was just thinking if he/she got transferable licenses he/she wanted to save) - a fresh start is best!!!!

I agree. Better safe than sorry, I always say. 🙂

What is the exact model or model ID: To find the model identifier open System Profiler in the Utilities folder. It's displayed in the panel on the right.

Should they have come with it?

Only if the computer shipped with 10.6 or earlier.

Follow Kappy's request to specifically identify your Mac model, otherwise we can only guess at the correct response for your issue.