You can easily add a TXT to just the domain name itself using the following steps:
- Login to your control panel
- Click Accounts & Settings and then click Domains
- Look to the right of the page (sidebar) and click Custom DNS Records option
- Scroll down to the TXT field and under "Type the name", leave the field empty. Type the value and click "Add TXT Resource Record".
Here’s a screenshot of how it should look:
Congratulations! You have successfully added a TXT record to just the domain name itself!