docs: add multiple prefix and fromExisting() documentation

Added documentation for SearchIndex.fromExisting() and multiple prefix
support in the getting-started guide.

Changes:
- New section on loading existing indices with fromExisting()
- New section on multiple prefix support with YAML and Java examples
- Note about prefix preservation when loading from Redis
- Explanation of getPrefix() behavior with multiple prefixes

Completes documentation for feat commit 3f37c52

Author: bsbodden

core/src/main/java/com/redis/vl/schema/IndexSchema.java

@@ -568,7 +568,7 @@ public static class Index {
     private String name;
 
     /**
-     * The prefix(es) used for Redis keys. Can be either a String (single prefix) or List<String>
+     * The prefix(es) used for Redis keys. Can be either a String (single prefix) or List of String
      * (multiple prefixes). Python port: supports Union[str, List[str]] for compatibility.
      */
     private Object prefix;
@@ -624,12 +624,12 @@ public String getPrefix() {
     }
 
     /**
-     * Get the raw prefix value (can be String or List<String>).
+     * Get the raw prefix value (can be String or List).
      *
      * <p>This method returns the prefix exactly as stored, without normalization. Use {@link
      * #getPrefix()} for the normalized prefix used in key construction.
      *
-     * @return the raw prefix (String or List<String>), or null if not set
+     * @return the raw prefix (String or List of String), or null if not set
      */
     public Object getPrefixRaw() {
       return prefix;

docs/content/modules/ROOT/pages/getting-started.adoc

@@ -150,6 +150,48 @@ SearchIndex index = new SearchIndex(schema, jedis);
 index.create(true);  // true = overwrite if exists
 ----
 
+=== Loading an Existing Index
+
+If you have an existing Redis index and want to load its schema:
+
+[source,java]
+----
+// Load schema from an existing Redis index
+SearchIndex index = SearchIndex.fromExisting("user-index", jedis);
+
+// The index object now has the schema loaded from Redis
+IndexSchema schema = index.getSchema();
+System.out.println("Index name: " + schema.getIndex().getName());
+System.out.println("Storage type: " + schema.getIndex().getStorageType());
+----
+
+NOTE: `fromExisting()` supports indices with multiple prefixes. If an index was created with multiple PREFIX values, all prefixes are preserved in the schema.
+
+=== Multiple Prefix Support
+
+RedisVL supports indices with multiple key prefixes:
+
+[source,yaml]
+----
+index:
+  name: multi-prefix-index
+  prefix: [user, customer, account]  # Multiple prefixes
+  storage_type: json
+----
+
+Or programmatically:
+
+[source,java]
+----
+IndexSchema schema = IndexSchema.builder()
+    .name("multi-prefix-index")
+    .prefix(List.of("user", "customer", "account"))  // Multiple prefixes
+    .storageType(IndexSchema.StorageType.JSON)
+    .build();
+----
+
+When using multiple prefixes, `getPrefix()` returns the first prefix for key construction, while all prefixes are preserved for schema comparison and serialization.
+
 == Load Data
 
 Load your data into Redis: