Add activation text

Author: kabilar

README.md

@@ -95,11 +95,14 @@ This ephys element features automatic ingestion for spike sorting results from t
 </details>
 
 ## Usage
-<details>
-<summary>Click to expand details</summary>
 
 ### Element activation
 
+When using this Element, one needs to run `ephys.activate` to declare the schemas and tables on the database.
+
+<details>
+<summary>Click to expand details</summary>
+
 To activate the `element-array-ephys`, ones need to provide:
 
 1. Schema names
@@ -119,12 +122,12 @@ For more detail, check the docstring of the `element-array-ephys`:
     help(probe.activate)
     help(ephys.activate)
 
+</details>
+
 ### Example usage
 
 See [this project](https://github.com/datajoint/workflow-array-ephys) for an example usage of this Array Electrophysiology Element.
 
-</details>
-
 ## Citation
 
 + If your work uses DataJoint and DataJoint Elements, please cite the respective Research Resource Identifiers (RRIDs) and manuscripts.