If you're using Givecloud as your main website and need to perform the Pinterest Verification process (https://help.pinterest.com/en/articles/verify-your-website), here's how to add the meta tag to your Givecloud Site:
Log into your Givecloud admin panel.
Go to Features > Site Design > Advanced.
Paste your Pinterest verification meta string into the "Custom HEAD Tags" section.
Go back to Pinterest and do the Complete Verification step.