Update README with setup instructions

README.md

@@ -2,3 +2,30 @@
 
 You can fork this repository and edit `feeds.toml` to start generating your own
 RSS feeds.
+
+# Automatically generate feeds
+
+## On GitHub
+
+To automatically generate feeds twice a day on GitHub:
+
+1. Fork this repository and edit `feeds.toml`.
+2. Create a branch called `gh-pages`.
+3. Visit [/actions](./actions), then enable workflows for your fork.
+
+GitHub Actions will then automatically run twice a day to check for updates,
+and publish your feeds at `https://<username>.github.io/feeds/`.
+
+## On GitLab
+
+To automatically generate feeds on GitLab:
+
+1. Fork this repository and edit `feeds.toml`.
+2. [Create a new pipeline schedule](./-/pipeline_schedules/new) (CI/CD ˃
+   Schedules).
+3. Set it to your desired interval (e.g. `30 5,17 * * *` to run at 5:30 and
+   17:30).
+4. Hit "Save pipeline schedule".
+
+GitLab CI/CD will then automatically run at your selected interval to check for
+updates, and publish your feeds at `https://<username>.gitlab.io/feeds/`.