Explicitly state CLA requirement

Author: zacharysarah

CONTRIBUTING.md

@@ -1,7 +1,11 @@
 # Contributing
 
-Welcome to Kubernetes! If you are interested in contributing to the [Kubernetes code repo](README.md) then checkout the [Contributor's Guide](https://git.k8s.io/community/contributors/guide/)
+Welcome to Kubernetes! To learn more about contributing to the [Kubernetes code repo](README.md), check out the [Contributor's Guide](https://git.k8s.io/community/contributors/guide/).
 
-The [Kubernetes community repo](https://github.com/kubernetes/community) contains information on how the community is organized and other information that is pertinent to contributing.
+The [Kubernetes community repo](https://github.com/kubernetes/community) contains information about how to get started, how the community organizes, and more.
+
+## Sign the CLA
+
+You must sign the [Contributor License Agreement](https://git.k8s.io/community/contributors/guide/getting-started.md#sign-the-cla) in order to contribute.
 
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