Your TXT records can be easily managed with the help of the Zone Editor section, which can be found at your control panel. Open your cPanel and find Domains → Zone Editor:
In order to create a TXT record, you just need to click on the button Manage:
Click on Add record option and change record type to TXT:
Add the values and click save
NOTE: Any DNS Record changes trigger propagation, which can last up to 24 hours to fully propagate.