Double-click the taskbar icon to open the Security Center
Click Advanced Menu (lower left)
Click Configure (left)
Click Computer & Files (upper left)
VirusScan can be disabled on the right.
Do the same via Internet & Network for Firewall Plus.
Found it at the McAfee forum:
When installing software or playing certain resource-intensive games, I'd like to disable McAfee temporarily. There no longer seems to be a rapid way to do this, but I'll bet there really is. Can anyone help?
-- Dave K.