There are multiple ways to integrate Java libraries into an Eclipse project. But the easiest one is to create at first a folder which will be named "libs". For this make right click on your Eclipse project and click on "New" -> "Folder".
After this copy the downloaded libraries into the created folder. Now the libraries are in the project but not in the build path. For adding the library to the project make a right click to the library and click on "Build Path". After this go to "Add to Build Path".
If you now get an error like this:
Project 'X' is missing required library: 'libs/spring-core-4.1.6.RELEASE.jar'
The project cannot be built until build path errors are resolved
Your project is missing in our case a spring library. The spring core library.
For avoiding this situation you can use a build tool like Maven. But especially for beginner's it is hard to set up Maven and creating a pom.xml and so on. Because of this will forget this approach. We go to the Download Area and we will finish the described steps on this page.
After we will get a ZIP file with all the needed JAR files. We will copy these JAR files in our "libs" folder. If we now do the following: "mark all new libraries" -> "right click on these libraries" -> "Build Path" -> "Add to Build Path". We should have resolved our build problems.