docs: explain how to use presets

docs/usage/config-presets.md

@@ -164,7 +164,7 @@ In short, the number of `{{argx}}` parameters in the definition is how many para
 Parameters must be strings, non-quoted, and separated by commas if there are more than one.
 
 If you find that you are repeating config a lot, you might consider publishing one of these types of parameterised presets yourself.
-Or if you think your preset would be valuable for others, please contribute a PR to the Renovate repository.
+Or if you think your preset would be valuable for others, please contribute a PR to the Renovate repository, see [Contributing to presets](#contributing-to-presets).
 
 ## GitHub-hosted Presets
 
@@ -213,6 +213,9 @@ Renovate will determine the current platform and look up the preset from there.
 Have you configured a rule that you think others might benefit from?
 Please consider contributing it to the [Renovate repository](https://github.com/renovatebot/renovate/tree/main/lib/config/presets/internal) so that it gains higher visibility and saves others from reinventing the same thing.
 
+Create a [discussion](https://github.com/renovatebot/renovate/discussions) to propose your preset to the Renovate maintainers.
+The maintainers can also help improve the preset, and let you know where to put it in the code.
+
 ## Organization level presets
 
 Whenever repository onboarding happens, Renovate checks if the current user/group/org has a default config to extend.

docs/usage/configuration-options.md

@@ -854,7 +854,8 @@ The above would mean Renovate would not include files matching the above glob pa
 
 ## extends
 
-See [shareable config presets](https://docs.renovatebot.com/config-presets) for details.
+See [shareable config presets](./config-presets.md) for details.
+Learn how to use presets by reading the [Key concepts, Presets](./key-concepts/presets.md/#how-to-use-presets) page.
 
 ## extractVersion
 

docs/usage/key-concepts/presets.md

@@ -16,6 +16,21 @@ Use presets to:
 - Share your configuration with others
 - Use somebody else's configuration and extend it with your own rules
 
+## How to use presets
+
+Let's say you're using the `config:base` preset, and want to pin your GitHub Action digests.
+Instead of writing your own Renovate config, you search through Renovate's built-in presets.
+You find the the `helpers:pinGitHubActionDigests` preset and add it to the `extends` array:
+
+```json
+{
+  "extends": ["config:base", "helpers:pinGitHubActionDigests"]
+}
+```
+
+Renovate now follows the rules for `config:base` plus the rules for `helpers:pinGitHubActionDigests`.
+If there is a logical conflict between presets, then the last preset in the array wins.
+
 ## Managing config for many repositories
 
 If you manage Renovate for many repositories, then you should create a global preset configuration.
@@ -32,6 +47,12 @@ Renovate comes with a lot of built-in presets that you can use.
 Browse [Renovate's default presets](https://docs.renovatebot.com/presets-default/) to find any that are useful to you.
 Once you find a preset you like, put it in an `extends` array in your config file.
 
+### Contributing a new built-in preset
+
+If you have a Renovate config that may help others, you can put it into Renovate's built-in presets.
+
+Read [Contributing to presets](./config-presets.md#contributing-to-presets) to learn how.
+
 ## Summary
 
 In short: