YouTube restricts the links you can insert in your video: these can point towards your website, or towards a list of crowdfunding platforms, which Ulule is part of.
This option is only available if your Youtube channel reaches at least 10000 public views.
Hence, you can add a link to your campaign inside your video and incite your audience to click on it.
Make sure to broadcast your video only once your campaign is published, so that your contributors land on an available page.