Add applying brand section

Author: cwickham

docs/authoring/brand.qmd

@@ -59,6 +59,8 @@ View the example: [Source](https://github.com/cwickham/quarto-examples/tree/bran
 
 On this page:
 
+-   Learn how to add a brand file
+
 -   Learn about the elements of **brand.yml** and how they are used in Quarto.
 
 -   Learn how to access brand values outside of the brand file.
@@ -73,6 +75,46 @@ The **brand.yml** specification is an active area of work at Posit. Quarto's sup
 Currently, the formats that support **brand.yml** are: `html`, `dashboard`, `revealjs` and `typst`.
 :::
 
+## Applying Brand
+
+To specify a brand, create a `_brand.yml` file in the root directory of your project. *Do you need a project? Do we reccommend a project? *
+Quarto will detect the presence of `_brand.yml` and automatically apply the brand to all documents of the supported formats in the project.
+
+You can also set, or override, brand settings in a document by specifying brand elements under the `brand` option:
+
+```{.yaml filename="document.qmd"}
+---
+brand:
+  color:
+    background: "#ffffff"
+---
+```
+
+You can disable brand for a document by setting `brand: false`:
+
+```{.yaml filename="document.qmd"}
+---
+brand: false
+---
+```
+
+You can put  `_brand.yml` in a subdirectory of your project, and then use the `brand` key to specify the path to the brand file.
+For example, to the the brand file at `brand/_brand.yml` for a single  document, add `brand` to the header:
+
+```{.yaml filename="document.qmd"}
+---
+brand: brand/_brand.yml
+---
+```
+
+To use the brand file at `brand/_brand.yml` for all documents in the project add `brand` to `_quarto.yml`:
+
+```{.yaml filename="_quarto.yml"}
+brand: brand/_brand.yml
+```
+
+Paths specified in `_brand.yml` are relative to the location of the brand file. (*Is this true?*)
+
 ## Brand Elements
 
 The elements of **brand.yml** are specified in the specification at <https://posit-dev.github.io/brand-yml/>. In this section, learn how these elements are used in Quarto.