Payroll and Invoicing - intuitive systems?

[mylittleyumyum]

I have a knowledge gap when it comes to payroll and invoicing.

I'm applying for administration roles, which used to be my specialty, but I'm finding that these are pretty necessary skills as many smaller companies don't have separate finance departments.

How do I garner some knowledge in these fields in lieu of on the job experience? I'm working full time at the moment in a different field.

I have started an online course on Xero, which I have seen mentioned on some job specs.