Update custom fields docs

docs/advanced_usage.md

@@ -619,24 +619,3 @@ single-sided split marker page, the split document(s) will have an empty page at
 whatever else was on the backside of the split marker page.) You can work around that by having
 a split marker page that has the split barcode on _both_ sides. This way, the extra page will
 get automatically removed.
-
-## Custom Fields {#custom-fields}
-
-Paperless allows the addition of custom fields to be attached to documents, allowing a user
-to optionally include additional data which does not fit in the existing set of metadata
-Paperless provides.
-
-First, the user creates a custom field, with a given name and data type. This could be
-something like "Invoice Number", with a data type of "Number". This allows
-reuse of the same name and data type, obviating the need to type the same name again and
-again, instead selecting.
-
-Next. the field may be used with a particular document and custom data stored. The data
-stored is required to match the chosen data type for the field.
-
-Multiple fields may be attached to a document. The same field name cannot be assigned multiple
-times to a document, so you cannot use "Invoice Number" twice **on the same document**.
-
-!!! note
-
-    Once the data type for a field is set, it cannot be changed again.

docs/usage.md

@@ -322,6 +322,28 @@ applied. You can use the following placeholders:
 - `{added_month_name_short}`: added month short name
 - `{added_day}`: added day
 
+## Custom Fields {#custom-fields}
+
+Paperless-ngx supports the use of custom fields for documents as of v2.0, allowing a user
+to optionally attach data to documents which does not fit in the existing set of fields
+Paperless-ngx provides.
+
+1. First, create a custom field (under "Manage"), with a given name and data type. This could be something like "Invoice Number" or "Date Paid", with a data type of "Number", "Date", "String", etc.
+2. Once created, a field can be used with documents and data stored. To do so, use the "Custom Fields" menu on the document detail page, choose your existing field and click "Add". Once the field is visible in the form you can enter the appropriate
+   data which will be validated according to the custom field "data type".
+3. Fields can be removed by hovering over the field name revealing a "Remove" button.
+
+!!! important
+
+    Added / removed fields, as well as any data is not saved to the document until you
+    actually hit the "Save" button, similar to other changes on the document details page.
+
+!!! note
+
+    Once the data type for a field is set, it cannot be changed.
+
+Multiple fields may be attached to a document but the same field name cannot be assigned multiple times to the a single document.
+
 ## Best practices {#basic-searching}
 
 Paperless offers a couple tools that help you organize your document