To open a CMake project in Eclipse CDT, you first need to configure and generate a project from your CMake files.
I described how to generate your files with CMake GUI here. This post assumes you generated your project with the Eclipse CDT generator.
Import the project
Click File -> Open Projects from File System…
Choose the directory you generated your CMake files in the next dialog. Eclipse project should appear under Import as.
If Eclipse does not get your project double check the previous steps e.g. chosen generator, selected directory etc.
Click Finish to complete the import.
You can add your project to a Working Set. You can create these to group your projects and help to keep an overview inside your workspace. You may as well skip that in the import-dialog, as you can switch assignments later, too.
After the import open the Project Explorer.
You can now start to work on your source files, listed under [Source directory].
Binaries holds a list of all your binaries built by the project.
To build / clean the whole project, the target is provided in the root Build Targets. To build individual targets only, go to [Targets] or the Build Targets tab.