docs: added a note linking to create-medusa-app reference (#12950)

* docs: added a note linking to create-medusa-app reference

* Update page.mdx

Author: shahednasser

www/apps/book/app/learn/installation/page.mdx

@@ -35,6 +35,12 @@ npx create-medusa-app@latest my-medusa-store
 
 Where `my-medusa-store` is the name of the project's directory and PostgreSQL database created for the project. When you run the command, you'll be asked whether you want to install the Next.js Starter Storefront.
 
+<Note>
+
+To customize the default installation behavior, such as specify a database URL, refer to the [create-medusa-app reference](!resources!/create-medusa-app).
+
+</Note>
+
 After answering the prompts, the command installs the Medusa application in a directory with your project name, and sets up a PostgreSQL database that the application connects to.
 
 If you chose to install the storefront with the Medusa application, the storefront is installed in a separate directory named `{project-name}-storefront`.