This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
First step, like Jeanne mentioned, is to install the m2eclipse plugin. You can find it in the Eclipse marketplace - just do a search on "maven". Once that is installed, within Eclipse do File | Import | Maven |Existing Maven Projects. Then you are all set to go.
Though looking at the ling you provided, all of the projects stored in appear to be Eclipse projects. For example, https://src.springframework.org/svn/spring-samples/petcare/trunk/ has both a .project and a .classpath file. In that case, after installing m2eclipse you can import the project using File Import | Existing Projects into Workspace.