Add your wakatime api key from here, in your repository secrets with the name WAKATIME_API_KEY.

Optional: If you are adding this action to a repository other than your profile repository (<username>/<username>), add your Github API Token from here, in your repository secrets with the name GITHUB_TOKEN.

Go to actions tab of your repository, click New workflow, and then click the link set up a workflow yourself.

Replace all the file contents with the following:

name: Wakatime Charts

on:
  workflow_dispatch:
  schedule:
    - cron: "0 0 * * *"

jobs:
  update-charts:
    name: Update wakatime stats charts
    runs-on: ubuntu-latest
    steps:
      - uses: divykj/wakatime-charts@master
        with:
          WAKATIME_API_KEY: ${{ secrets.WAKATIME_API_KEY }}
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} # only required if using the action in repository other than profile

Commit this workflow file.