Ok I’ll just explain a couple of things.
As a Sole Trader the Government/Revenue don’t differentiate you from your business. That’s the key difference between Sole Trader and Limited Company. A Limited Company is a separate entity to you, but as Sole Trader isn’t.
You can’t put money “into”, the business, what you’re thinking of is as a Limited business you can put money into the business and take it out tax free, so before tax.
If you want to start an opening balance in Bullet just create your bank account (good practice to setup a new one for your business) and create an opening balance.
You can do that here My Company > Bank Accounts > Create New Account
How to create an opening bank balance in Bullet free online accounting software
So you’re quite right Sole Traders can’t use payroll to pay themselve but you as a sole trader can still have employees, therefore you’ll need payroll to pay them.
Hope that helps.