Step description updates (#58)

* Step description updates

* updated step description

based on review comments

Author: BanyikAnna

step.yml

@@ -1,9 +1,27 @@
 title: Carthage
 summary: |-
-  Runs selected Carthage command.
+  Runs the selected Carthage command.
 description: |-
-  Runs selected Carthage command. The step will cache your dependencies only when using `bootstrap` as `carthage_command` and you have `cache-pull` and `cache-push` steps in your workflow.
-  For more information about Carthage, visit the [Carthage GitHub page](https://github.com/Carthage/Carthage).
+  Downloads and builds the dependencies your Cocoa application needs.
+  
+  ### Configuring the Step
+  1. Add the **Carthage** Step in your Workflow.
+  2. Select `bootstrap` Carthage command in the **Carthage command to run** input. Make sure you have the **Bitrise.io Cache:Pull** Step before and the **Bitrise.io Cache:Push** Step after the **Carthage** Step in your Workflow to cache files and speed up your Bitrise build.
+  2. Provide your GitHub credentials in the **GitHub Personal Access Token** input to avoid GitHub rate limit issues. Don't worry, your credentials are safe with us since we store them encrypted and do not print them out in build logs.
+  3. Optionally, you can provide any extra flag for the Carthage command you wish to run in the **Additional options for Carthage command** input.
+  5. To get more information printed out, set the **Enable verbose logging** to `yes`.
+
+  ### Troubleshooting
+  It is important that you use `bootstrap` Carthage command, as this is the only command that can leverage the cache! If you run, for example, the `update` command, it won't generate the required cache information, because the `update` command will disregard the available files or the cache.
+
+  ### Useful links
+  - [Official Carthage documentation](https://github.com/Carthage/Carthage)
+  - [About Secrets and Env Vars ](https://devcenter.bitrise.io/builds/env-vars-secret-env-vars/)
+
+  ### Related Steps
+  - [Bitrise.io Cache Push](https://www.bitrise.io/integrations/steps/cache-push)
+  - [Bitrise.io Cache Pull](https://www.bitrise.io/integrations/steps/cache-pull)
+  - [iOS Auto Provision](https://www.bitrise.io/integrations/steps/ios-auto-provision)
 website: https://github.com/bitrise-steplib/steps-carthage
 source_code_url: https://github.com/bitrise-steplib/steps-carthage
 support_url: https://github.com/bitrise-steplib/steps-carthage/issues