Add build steps for contributions pages

CONTRIBUTING.md

@@ -7,6 +7,19 @@ Thanks for your help improving the project!
 If you have a question about Kubecost or have encountered problems using it,
 you can start by asking a question on [Slack](https://join.slack.com/t/kubecost/shared_invite/enQtNTA2MjQ1NDUyODE5LTg0MzYyMDIzN2E4M2M5OTE3NjdmODJlNzBjZGY1NjQ3MThlODVjMGY3NWZlNjQ5NjIwNDc2NGU3MWNiM2E5Mjc) or via email at [team@kubecost.com](team@kubecost.com)
 
+## Building ## 
+
+Follow these steps to build from source and deploy:
+
+1. `docker build --rm -f "Dockerfile" -t <repo>/kubecost-cost-model:<tag> .`
+2. Edit the [pulled image](https://github.com/kubecost/cost-model/blob/master/kubernetes/deployment.yaml#L22) in the deployment.yaml to <repo>/kubecost-cost-model:<tag>
+3. Set [this environment variable](https://github.com/kubecost/cost-model/blob/master/kubernetes/deployment.yaml#L30) to the address of your prometheus server
+4. `kubectl create namespace cost-model`
+5. `kubectl apply -f kubernetes/ --namespace cost-model`
+6. `kubectl port-forward --namespace cost-model service/cost-model 9003`
+
+To test, you'll need to build the cost-model docker container then push it to a kubernetes cluster with a running prometheus.
+
 ## Certification of Origin ##
 
 By contributing to this project you certify that your contribution was created in whole or in part by you and that you have the right to submit it under the open source license indicated in the project. In other words, please confirm that you, as a contributor, have the legal right to make the contribution.