Update fastbuild.md

docs/fastbuild.md

@@ -1,8 +1,20 @@
+## Fast Build
+
+The IntelliJ plugin for Bazel includes the **Fast Build** feature, allowing you to run tests and executables without recompiling the entire target. This feature detects which Java files have changed and compiles only those files, significantly speeding up the development process.
+
 ## Requirements
-In order to get fast build working, you have to add some VM options to the IntelliJ setup.
-You can go to Help -> Edit custom VM options, and add these entries there:
-```
+
+To enable Fast Build, you must add specific VM options to your IntelliJ configuration. Follow these steps:
+
+1. Navigate to **Help** -> **Edit Custom VM Options**.
+2. Add the following entries:
+
+```plaintext
 --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED
 --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED
 --add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED
 ```
+
+## How to Use
+
+To use Fast Build, locate your test or executable in the editor. Click the gutter icon and select either **Fast Run** or **Fast Test**.