To verify (claim) your website on Pinterest, go to Settings → Claimed accounts, click Claim next to Website, and choose one of three methods: add an HTML tag, upload an HTML file, or add a DNS TXT record. Follow Pinterest's steps for your chosen method, and your domain will be claimed once verified.
Visit your Pinterest account and go to Settings under 'Your accounts'.
Click Claimed Accounts on the left toolbar.
Next to 'Website', click Claim.
Then you will choose between three options on how you want to claim your domain: Add HTML tag, Upload HTML file, or Add TXT record.
Read more about Add HTML tag here: Add an HTML tag to your website
Read more about Upload HTML file here: Upload an HTML file to your website
Read more about Add TXT record here: Add a DNS TXT record to your domain host
Follow the steps provided depending on which method you choose.