Add to the docs for compleseus about selecting a completion engine

layers/+completion/compleseus/README.org

@@ -6,10 +6,11 @@
 - [[#description][Description]]
   - [[#features][Features:]]
 - [[#install][Install]]
+  - [[#configuration][Configuration]]
 - [[#key-bindings][Key bindings]]
 
 * Description
-This layer adds a new way of completion provided by the following core packages: 
+This layer adds a new way of completion provided by the following core packages:
 - =consult=
 - =embark=
 - =marginalia=
@@ -31,6 +32,13 @@ commented out in the =dotspacemacs-configuration-layers= list. Or add
 =compleseus= below the other completion layers. Spacemacs uses the completion
 layer that's listed last.
 
+** Configuration
+
+You can configure the completion engine by setting =compleseus-engine= to either =vertico= (default) or =selectrum=  by editing the =compleseus-engine= variable like below to use =selectrun as opposed to the default of =vertico=:
+
+#+BEGIN_SRC emacs-lisp
+  (compleseus :variables compleseus-engine 'selectrum)
+#+END_SRC
 * Key bindings
 
 | Key binding | Description   |