Your TXT records can be easily managed with the help of the Zone Editor section, which can be found in 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 the record type to TXT:
Once created, Zone Editor section provides you with these buttons for already created TXT records:
Button to edit your TXT records
Button for deleting your TXT records completely
NOTE
Any changes in the DNS zone trigger propagation, which can last up to 24 hours to fully propagate