Your A 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 an A record, you just need to click on the button + A RECORD:
Choose domain Name value and Address (it has to be IPv4 address):
Zone Editor section provides you with these buttons for already created A records:
Button to edit your A records
Button for deleting your A records completely
Any DNS Record changes trigger propagation, which can last up to 24 hours to fully propagate.