Update docs for exploring ASTs

docs/codeql/codeql-for-visual-studio-code/exploring-the-structure-of-your-source-code.rst

@@ -18,20 +18,26 @@ CodeQL for Visual Studio Code contains an AST viewer. The viewer consists of a g
 Viewing the abstract syntax tree of a source file
 --------------------------------------------------
 
-1. Open a source file from a CodeQL database. For example, you can navigate to a source file in the File Explorer.
+1. Open the CodeQL Databases view and right-click the database that you want to explore. Click **Add Database Source to Workspace**.
+
+   .. image:: ../images/codeql-for-visual-studio-code/add-database-source-to-workspace.png
+      :width: 350
+      :alt: Add database source to workspace
+
+2. Navigate to a source file  from a CodeQL database in the File Explorer.
 
    .. image:: ../images/codeql-for-visual-studio-code/open-source-file.png
       :width: 350
       :alt: Open a source file
 
-2. Run **CodeQL: View AST** from the Command Palette. This runs a CodeQL query (usually called ``printAST.ql``) over the active file, which may take a few seconds.
+3. Run **CodeQL: View AST** from the Command Palette. This runs a CodeQL query (usually called ``printAST.ql``) over the active file, which may take a few seconds.
    
    .. pull-quote:: Note
 
       If you don't have an appropriate ``printAST.ql`` query in your workspace, the **CodeQL: View AST** command won't work. To fix this, you can update your copy of the `CodeQL <https://github.com/github/codeql>`__ repository from ``main``. If you do this, you may need to upgrade your databases. Also, query caches may be discarded and your next query runs could be slower.
 
-3. Once the query has run, the AST viewer displays the structure of the source file.
-4. To see the nested structure, click the arrows and expand the nodes.
+4. Once the query has run, the AST viewer displays the structure of the source file.
+5. To see the nested structure, click the arrows and expand the nodes.
 
    .. image:: ../images/codeql-for-visual-studio-code/explore-ast.png
       :alt: Explore the AST