antivirus, spyware and firewalls?

I really am pretty stupid when it comes to antivirus software. I
recently purchased the full paid version of malwarebytes. I would like
to scrap McAfee and try the windows security essentials in its place
but am not sure if it replaces the malwarebytes or if the two can run
at the same time. Also do i still need a firewall program and which
would be compatable with malwarebytes and windows security essentials.
These are probably really dumb questions but I am old and truly computer
stupid. Any advice?
You can run MBAM alongside MS Security Essentials.

You do not
really need a firewall, because Windows already has one. However, this
firewall is a bit weak. You can install a third party firewall, if your
computer is up to the task of running this extra software. The following
software firewalls are good and free:

• Comodo Firewall. Install the internet security suite, but without the antivirus and without the Hopsurf toolbar.
  
• Online Armor. A very smart and user friendly firewall.
  
• Outpost Firewall is another rocksolid choice.
  

These
firewalls should all work problemless alongside MBAM and MS Security
Essentials. And if it does not, uninstall it and pick another one from
the list.