First, submit your changes to update the code snippet and make sure you have created the form you want to see - check the preview window to see all spelling is correct and any other parameters.
If you make any changes, update the snippet again and when you are happy, copy the snippet.
The embed that code snippet into your website.
The exact instructions differ for the various website management tools. You can check their website help guides below to get more information on how to do this for your site.
Wordpress
WordPress.com Support — General help with WordPress.com sites.
WordPress.org Support —General help with WordPress.org sites.
Managing Plugins — How to managing WordPress plugins (like the Better Giving plugin).
Wix
Wix Help Center — General help with Wix.
Wix Editor: Using iFrames to Display Visible Content on Your Site — How to work with iFrames in Wix.
Webflow
Webflow University — General help with Webflow sites.
Custom code embed — Creating code snippet embeds in Webflow.
Weebly
Weebly Support - General help with Weebly sites
Weebly help guide - Embed widget/code onto a Weebly page
Squarespace
Squarespace Help — General help with Squarespace sites.
Adding custom code to your site — How to add custom code to a Squarespace site.