I'm a bit confused about what you're asking for.
After setting up the sfPropelORMPlugin and making sure it's configured correctly, you'll want to execute this command to move (or create a symlink to) the css files into the web folder:
php symfony plugins:publish-assets
Once that's done, you should see the css files in the /web directory, just like you mentioned /web/sfPropelORMPlugin/css/...
.
The stylesheets from sfPropelORMPlugin will automatically be included in your admin generator module and crud module. However, if you need them in a different location (such as a custom module), you can simply include them like regular css files:
<link rel="stylesheet" type="text/css" href="/sfPropelORMPlugin/css/global.css" />
<link rel="stylesheet" type="text/css" href="/sfPropelORMPlugin/css/default.css" />