If you need to modify a DNS record, you should first log in to your cPanel.
Once in your cPanel, you should visit the "Zone Editor" icon.
After that, click the "Manage" link next to the domain you wish to modify DNS records for. You can choose to filter records by CNAME, A, AAAA, MX, SRV, or TXT. You can click the "Add Record" button to add a new DNS record.
Please note that if you are doing something like changing a DNS record to point somewhere else, you should probably delete the existing DNS record first.