Q: how to format macbook pro

Your Mac can accept 16 GB (2x8 GB). I would replace one 2 GB stick with one 8 GB stick.

This place sells compatible memory and provides installation videos

https://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade/DDR3_13 33MHz_SDRAM

First make sure that your Mac has the EFI firmware update that adds Internet Recovery

Computers that can be upgraded to use OS X Internet Recovery - Apple Support

What OSX version is now on the Mac?

Without knowing that I would boot to Internet Recovery

About OS X Recovery - Apple Support

try holding down Option-Command-R to start up from OS X Internet Recovery*.

Then format the startup disk and install Lion. Then yo can update to EL Capitan (and maybe others depending upon what OSX version were previously used on the Mac/your ID)

This is the Mac Pro desktop forum. I requested your post be moved to the MacBook Pro laptop forum or other appropriate forum.