Add page on subscriptions

Author: PhilReedData

TeSS_docs/_toc.yml

@@ -9,6 +9,7 @@ parts:
     - file: overview/tess
     - file: overview/definitions
     - file: overview/what-we-catalogue
+    - file: overview/subscribe
   - caption: Account creation
     chapters:
     - file: accounts/user

TeSS_docs/images/overview/subscription.png

@@ -0,0 +1,31 @@
+# Subscribing to notifications
+
+TeSS also provides a subscription feature to help users to stay informed about courses, workshops and conferences of interest to them. 
+The service may be customised by selecting the relevant filters, and initiated via the subscribe button. 
+Users may choose to receive email notifications about upcoming events, or have them automatically added to their preferred calendar application.
+
+## Adding scriptions
+
+To add a scription:
+
+1. Apply a choice of filters to show the type of events you are interested in.
+2. Click the 'Subscribe' button near the top of the results to email alerts or track events in your calendar application.
+
+::::{grid} 1 1 2 2
+:class-container: sd-border-0
+
+:::{grid-item}
+:columns: 10
+[![Subscriptions manager page](../images/overview/subscription.png)](../images/overview/subscription.png)
+:::
+::::
+
+## Managing subscriptions
+
+The subscriptions manager page may be used to change the frequency of, or to remove, subscriptions.
+
+To find the subscriptions manager page:
+
+1. If you have not yet logged in, in the top menu, click 'Log In'.
+2. In the top menu, click your username, then click 'My profile'.
+3. At the top-right, click the 'Manage subscriptions' button.