Your can easily manage the A records of your domain with the help of the Zone Editor section. Just log in to your cPanel and find Domains → Zone Editor:
To create an A record, click on the button + A RECORD:
Enter the domain or subdomain name on the Name field and the IPv4 address on the Address field, then click on ADD AN A RECORD:
On the Zone Editor section you can also manage your records using the following buttons:
Edit an A record
Permenently delete an A record
NOTE
Any DNS Record changes trigger propagation, which can last up to 24 hours to complete