Here are the links at 1&1 hosting that explain how to:
Setup an A Record
Change your CNAME
Links now dead
1&1 updated their service... You can no longer change A-records and C-name. You need to edit your service so we use your name servers instead.
Links have been updated to 1&1 support forums with the correct instructions
The problem isn't the links. 1 & 1 doesn't allow you a custom C-name and custom A-record at the same time, I've already called them twice about it.
True, you have to choose either CNAME or DNS
So I changed my A-Record (cannot add one under 1and1 - It shows in Incapsula that it has been changed, but obviously the CNAME isn't... It say's PENDING DNS CHANGE at the top in red, but I can reach my site through the Incapsula IP address and CNAME, how can I tell if it is actually working?
If you're trying to use both Incapsula and 1&1, it isn't working Nate. You're going to have to move you're site away from 1&1. They just don't allow you to do both a c-name and an a-record change. They told me it's just not possible and were unwilling to discuss the issue further.
We went to DomainFactory, because 1&1 and many other german-based hoster does not allow to add a second A-Record neither to change the CNAME entry.