Explain how to add a search engine to Vanadium and set as default

static/usage.html

@@ -601,6 +601,27 @@ <h2><a href="#web-browsing">Web browsing</a></h2>
                 sites from each other rather than only containing content as a whole. The sandbox
                 has been gradually improving on the desktop but it isn't happening for their
                 Android browser yet.</p>
+
+                <p>Vanadium supports adding search engines through the <a
+                href="https://developer.mozilla.org/en-US/docs/Web/OpenSearch">OpenSearch</a> format.
+                To add a search engine and set it as the default search engine, the process is as
+                follows:</p>
+
+                <ol> 
+                    <li>Go to the website and perform a search.</li> 
+                    <li>Go to <strong>Settings > Search Engine</strong> and set the search engine 
+                    which now appears under <strong>Recently Visited</strong> as the default search 
+                    engine.</li> 
+                </ol>
+
+                <p>If the search engine does not appear even after performing a search, it may be
+                using POST HTTP requests by default to handle your queries, even if the website serves
+                an OpenSearch Document. For Vanadium to detect the search engine, queries need to be
+                made with GET HTTP requests.</p>
+
+                <p>If you have turned on GET HTTP requests with the search engine and Vanadium still
+                does not detect the search engine, it likely does not serve an OpenSearch document, and 
+                cannot be added as a search engine.</p>
             </section>
 
             <section id="camera">