Let's perform the following steps to build a custom Helm chart to be published in your local chartmuseum repository:

1. Create a chart called mychart:

$ helm create mychart

2. Edit your chart structure as you like and test the templates for possible errors:
   

$ helm lint ./mychart
==> Linting ./mychart
[INFO] Chart.yaml: icon is recommended
1 chart(s) linted, no failures

3. Test your application using --dry-run:

$ helm install ./mychart --debug --dry-run

4. Build the Helm chart. By running the following command, you will generate a tarball package of your Helm repository from the mychart location:

$ helm package .

5. Replace the Helm repository server address with your Helm server and upload this Helm chart package using a URL:

$ cd mychart && curl --data-binary "@mychart-0.1.0.tgz" http://10.3.0.37:8080/api/charts

Now you have learned how to create, lint, test, package, and upload your new chart to your local ChartMuseum-based Helm repository.