How do I change Avast so that I can install some software ?

I need to install a development server (xampps) onto my Windows 7 PC.
But when I try to install xampps it says that it has detected my anti-virus software, which may slowdown or damage the install, and that I should…

‘Add exceptions in the firewall: for Apache, MySQL or any other server.
Scan files when executing: If you have enabled the anti-virus scan for all files, the executable files for the servers may slow down.
Scan the traffic for different URLs: If you are developing with XAMPP on your own machine, you can exclude “localhost” traffic in the Anti-virus settings.’

So how do I do this in Avast ??
and in my Windows 7 Firewall ??

Thanks

Do this only if you know it’s safe!

GUI>Settings>Antivirus>Exclusions