Update CONTRIBUTING.md with instructions on releasing specs

CONTRIBUTING.md

@@ -91,6 +91,22 @@ cabal configure <package-name> --ghc-options="-Wwarn"
 cabal build <package-name>
 ```
 
+## Publishing specifications
+PDF specs are stored as attachments to [github releases](https://github.com/input-output-hk/cardano-ledger/releases)
+We can create a release that builds and attaches the latest specs, by triggering the [push-docs github action](https://github.com/input-output-hk/cardano-ledger/blob/master/.github/workflows/push-specs.yml).
+This github action can be triggered by pushing a tag of the pattern: `cardano-ledger-spec-YYYY-MM-DD`, for example: `cardano-ledger-spec-2023-01-17`
+
+For example, if we decide it's time to publish new versions of docs,
+we can do the following to publish the PDFs under release `cardano-ledger-spec-2023-03-21`:
+```
+git tag cardano-ledger-spec-2023-03-21
+git push origin cardano-ledger-spec-2023-03-21
+```
+
+This will create a new release that will be available as [latest](https://github.com/input-output-hk/cardano-ledger/releases/latest).
+Make sure that the `YYYY-MM-DD` part in the tag name is alphabetically greater than the rest, otherwise the release won't be tagged as `latest`.
+Using the current date should ensure that this is the case.
+
 ## Testing the Haskell programs
 
 The tests can be run with cabal.