Below are steps you should take for adding meta tag to a homepage of your Wordpress site to verify its ownership:
Note: the following steps are to verify your wordpress site for performing a crawl for it using Ahrefs Site Audit tool only!
Go to your Wordpress site's admin page
Go to Plugins and add the Meta Tag Manager plugin
After adding the plugin, go to Pages -> Home page and click Edit
4. In Site Audit, copy the HTML tag in the Project's Settings -> Ownership verification menu under HTML tag and paste it in the Meta Tag Manager in Wordpress
e.g.
<meta name="ahrefs-site-verification" content="xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx">
5. Click Update in Wordpress admin
6. Click Check Status in Ownership verification menu of Site Audit tool. Verification status should change to "Verified"
Note: If the Meta Tag Manager plugin doesn't work for you, look for a different plugin that adds the code to the header of your website's homepage.