How to install the Ad Up Plug In:
Dowload the plugin through this link (https://adup.io/plugins/woocommerce/ad-up-checkout.zip). Go to your WooCommerce backend and go to Plugins. Click on Add New
Click on Upload Plugin, upload the file you have downloaded and install the plugin.
Finally go to Ad Up settings on the left, fill in your company and change the colour of the Fast Checkout Button. Select how you want to use the Fast Checkout. Save the settings and Ad Up is available on your webshop.