Docs: Use memory (#12599)

### What problem does this PR solve?


### Type of change


- [x] Documentation Update

docs/guides/agent/agent_component_reference/message.mdx

@@ -21,3 +21,9 @@ The message to send out. Click `(x)` or type `/` to quickly insert variables.
 
 Click **+ Add message** to add message options. When multiple messages are supplied, the **Message** component randomly selects one to send.
 
+### Save to memory
+
+Select the corresponding Memory in the **Message** component under **Save to Memory**:
+
+
+![](https://raw.githubusercontent.com/infiniflow/ragflow-docs/main/images/save_to_memory.png)

docs/guides/agent/agent_component_reference/retrieval.mdx

@@ -76,13 +76,15 @@ Select the query source for retrieval. Defaults to `sys.query`, which is the def
 
 The **Retrieval** component relies on query variables to specify its queries. All global variables defined before the **Retrieval** component can also be used as queries. Use the `(x)` button or type `/` to show all the available query variables.
 
-### Knowledge bases 
+### Retrieval from
 
-Select the dataset(s) to retrieve data from.
+Select the dataset(s) and memory to retrieve data from.
 
 - If no dataset is selected, meaning conversations with the agent will not be based on any dataset, ensure that the **Empty response** field is left blank to avoid an error.
 - If you select multiple datasets, you must ensure that the datasets you select use the same embedding model; otherwise, an error message would occur.
 
+![](https://raw.githubusercontent.com/infiniflow/ragflow-docs/main/images/retrieve_from_memory.PNG)
+
 ### Similarity threshold
 
 RAGFlow employs a combination of weighted keyword similarity and weighted vector cosine similarity during retrieval. This parameter sets the threshold for similarities between the user query and chunks stored in the datasets. Any chunk with a similarity score below this threshold will be excluded from the results.