Before you can really employ an
IDE such as Eclipse effectively, you need to understand how the project is constructed without an IDE. And, as you can see, when people make their project build processes dependent on stuff that they've done to
their IDE and/or local filesystem, you can end up wasting a lot of time. Which is why I have a firm policy myself that every project must be buildable without an IDE or GUI using an offline tool such as
Ant or Maven.
You don't "import a WAR" into Eclipse. A WAR is the
output - the end product - of a build process. You start with a
project, you build the project, and produce the WAR, which is then deployed locally or on some other machine's web application server.
Eclipse has a project property that determines where compiled classes are placed. If you had been given the full source for an Eclipse project, it would have included a ".project" file that included the path of that location. You can set it by bringing up the Eclipse project Properties dialog, going to the "Build" tab and defining the source and destination folders for building on that tab.
Take a look there. Chances are you'll have further questions. We'll be here, although you might also want to find a good book on Eclipse and/or on building
J2EE web projects.