Dell E6520 won't connect to N300 network

> Recently purchase a refurbished Dell E6520 laptop running windows 7
> pro. [...]

   Does it have an appropriate Wireless LAN option?

      https://www.dell.com/downloads/global/products/latit/en/latitude-e6520-specsheet.pdf

> [...] Attempted to connect to network but can't establish wireless
> connection on N300 router.

   "Attempted" how?  "Attempted" or "can't" is not a useful problem
description.  It does not say what you did.  It does not say what
happened when you did it.  As usual, showing actual actions with their
actual results (error messages, LED indicators, ...) can be more helpful
than vague descriptions or interpretations.

> In the device manager the Dell laptop has a Bluetooth wireless
> adapter. Don't know if that is the problem or what?

   It may not be a problem, but it's irrelevant to connecting to a
wireless router.

   Can you connect your laptop to any other wireless router?  If there's
no built-in wireless-network adapter, then you might want to look for a
USB-connected external adapter.