McAfee Security Scan Plus is a waste of time. It's not actually an anti-virus program itself; it's just a free utility that checks that you've got up-to-date security programs on your computer. You don't need it, so you can happily get rid of it. (However it's not actually causing any conflicts at the moment).
What you need on your computer is:
1. A firewall ;
2. An anti-virus program ; and
3. Anti-malware protection.
You should only ever have one firewall and one anti-virus program but you can have as many 'run on demand' anti-malware programs as you like (although one is usually adequate).
Taking those three things in turn:
1. You've got a firewall because Windows comes with one built into it. Most people are perfectly happy to stick with that one but some others prefer to use a free third-party firewall, such as that offered by Comodo:
https://personalfirewall.comodo.com/
It's theoretically better than the Windows firewall (as it offers better 'two-way' protection) but, as I've said, most people don't bother changing. [If you do install the Comodo firewall, it will automatically switch off the Windows one, so there won't be any conflicts].
2. Avast is an excellent anti-virus solution. (It's what I use). Stick with it.
3. Super Anti-Spyware is a well known, and generally well-recommended, anti-malware program. The free edition is (unlike your firewall or anti-virus program) only 'run on demand', so it will do absolutely nothing unless you actively run it occasionally. I suggest once per fortnight or immediately if either:
(a) you realise that you've clicked on something that you shouldn't have (such as an email attachment from an unknown source) ; or
(b) you start experiencing problems with pop-ups or other adware.
However Super Anti-Spyware isn't the free anti-malware program that's most frequently recommended in the technical press (or here on AB). That's Malwarebytes Anti-Malware:
https://www.malwarebytes.org/antimalware/
You might like to also download and install that one (ensuring that you deselect the pre-ticked option to take a free trial of the Premium version when you do so). It can't cause any conflicts with Super Anti-Spyware as they're both 'run on demand' only, so you'd never have them both running at the same time.
In short:
You don't really need to do anything but you might as well get rid of McAfee Security Plus, as it doesn't do anything useful.
If you're paranoid about security you could add the Comodo firewall - but most people wouldn't bother.
Keep Super Anti-Spyware and remember to run it occasionally. Consider supplementing it with Malwarebytes Anti-Malware - but you might not need it.