Hello, Paddy Carr.
I'll give a brief overview on QuickBooks Online's integration process.
QuickBooks Online Accountant (Ireland) depends on the third-party's capabilities to integrate their program. You'll want to contact Practice Ignition's support and check to see if they offer a direct integration service with QBOA.
If they don't offer, then you'll have the option to manually import the data from Practice Ignition software. You might want to check this article for more details about the process: Import data from other software into QuickBooks Online.
If you need help working with your clients, you can check out the guides from the Help Articles page. They contain guides to help you reconcile their bank accounts, add transactions and more.
Say the word if you have more questions about managing your data or in QuickBooks Online (and the Accountant counterpart). I'm here to help.